Selina solutions for Concise Chemistry [English] Class 10 ICSE chapter 5 - Mole concept and Stoichiometry [Latest edition]

State Gay-Lussac's law of combining volumes.

State : Avogadro's law

What do you mean by stoichiometry?

Define atomicity of a gas. State the atomicity of Hydrogen, Phosphorus and Sulphur.

Differentiate between N₂ and 2N.

Explain Why?

"The number of atoms in a certain volume of hydrogen is twice the number of atoms in the same volume of helium at the same temperature and pressure."

Explain Why?

"When stating the volume of a gas, the pressure and temperature should also be given."

Explain Why?

Inflating a balloon seems to violate Boyle's law.

Calculate the volume of oxygen at STP required for the complete combustion of 100 litres of carbon monoxide at the same temperature and pressure.

\[\ce{2CO + O2 → 2CO2}\]

200 cm³ of hydrogen and 150 cm³ of oxygen are mixed and ignited, as per the following reaction,

\[\ce{2H2 + O2  → 2H2O}\]

What volume of oxygen remains unreacted?

24 cc Marsh gas (CH₄) was mixed with 106 cc oxygen and then exploded. On cooling the volume of the mixture became 82 cc, of which, 58 cc was unchanged oxygen. Which law does this experiment support? Explain with calculations.

What volume of oxygen would be required to burn completely 400 ml of acetylene [C₂H₂]? Also calculate the volume of carbon dioxide formed.

\[\ce{2C2H2 + 5H2O -> 4CO2 + 2H2O(l)}\]

112 cm³ of H₂S(g) is mixed with 120 cm³ of Cl₂(g) at STP to produce HCl(g) and sulphur(s). Write a balanced equation for this reaction.

1250 cc of oxygen was burnt with 300cc of ethane [C₂H₆]. Calculate the volume of carbon dioxide formed:

\[\ce{2C2H6 + 7O2  -> 4CO2 + 6H2O}\]

What volume of oxygen at STP is required to affect the combustion of 11 litres of ethylene [C₂H₄] at 273°C and 380 mm of Hg pressure?

\[\ce{C2H4 + 3O2 → 2CO2 + 2H2O}\]

Calculate the volume of HCl gas formed and chlorine gas required when 40 ml of methane reacts completely with chlorine at S.T.P.

\[\ce{CH4 + 2Cl2 → CH2Cl2 + 2HCl}\]

What volume of propane is burnt for every 500 cm³ of air used in the reaction under the same conditions? (assuming oxygen is `1/5`th of air)

\[\ce{C3H8 + 5O2 → 3CO2 + 4H2O}\]

450 cm³ of nitrogen monoxide and 200 cm³ of oxygen are mixed together and ignited. Caclulate the composition of resulting mixture.

\[\ce{2NO + O2 → 2NO2}\]

If 6 liters of hydrogen and 4 liters of chlorine are mixed and exploded and if water is added to the gases formed, find the volume of the residual gas.

Ammonia may be oxidised to nitrogen monoxide in the presence of a catalyst according to the following equation.

\[\ce{4NH3 + 5O2 → 4NO + 6H2O}\]

If 27 litres of reactants are consumed, what volume of nitrogen monoxide is produced at the same temperature and pressure?

A mixture of hydrogen and chlorine occupying 36 cm³ was exploded. On shaking it with water, 4cm³ of hydrogen was left behind. Find the composition of the mixture.

What volume of air (containing 20% O₂ by volume) will be required to burn completely 10 cm³ of methane?

\[\ce{CH4 + 2O2 → CO2 + 2H2O}\]

\[\ce{2C2H2 + 5O2 -> 4CO2 + 2H2O}\]

LPG has 60% propane and 40% butane: 10 litres of this mixture is burnt. Calculate the volume of carbon dioxide added to atmosphere.

\[\ce{C3H8 + 5O2 → 3CO2 + 4H2O}\]

\[\ce{2C4H10 + 13O2 → 8CO2 + 10H2O}\]

200 cm³ of CO₂ is collected at STP when a mixture of acetylene and oxygen is ignited. Calculate the volume of acetylene and oxygen at STP. in original mixture.

\[\ce{2C2H2_{(g)} + 5O2_{(g)} → 4CO2_{(g)} + 2H2O_{(g)}}\]

You have collected

1. 2 litres of CO₂
2. 3 litres of chlorine
3.  5 litres of hydrogen
4. 4 litres of nitrogen and
5. 1 litre of SO₂,

under similar conditions of temperature and pressure. Which gas sample will have the greatest number of molecules? Justify your answer.

The gases chlorine, nitrogen, ammonia and sulphur dioxide are collected under the same conditions of temperature and pressure. The following table gives the volumes of gases collected and the number of molecules (x) in 20 litres of nitrogen. You are to complete the table giving the number of molecules in the other gases in terms of x.

1. If 150 cc of gas A contains X molecules, how many molecules of gas B will be present in 75 cc of B? The gases A and B are under the same conditions of temperature and pressure.
2. Name the law on which the above problem is based.

The relative atomic mass of Cl atom is 35.5 a.m.u. Explain this statement.

What is the value of Avogadro's number?

What is the value of molar volume of a gas at S.T.P?

Define or explain the term:

Vapour density

Define or explain the term:

Molar volume

Define or explain the term:

Relative atomic mass

Define or explain the term:

Relative molecular mass

Define or explain the term

Avogadro's number

Define or explain the term:

Gram atom

Define or explain the term:

Mole

What are the main applications of Avogadro's Law?

How dose Avogadro's Law explain Gay-Lussac's Law of combining volumes?

Calculate the relative molecular mass of:

Ammonium chloroplatinate (NH₄)₂ PtCl₆

Calculate the relative molecular mass of:

Potassium chlorate

Calculate the relative molecular mass of:

CuSO₄. 5H₂O

Calculate the relative molecular mass of:

(NH₄)₂SO₄

Calculate the relative molecular mass of:

CH₃COONa

Calculate the relative molecular mass of:

CHCl₃ 

Calculate the relative molecular mass of:

(NH₄)₂ Cr₂O₇

Find the number of molecules in 73 g of HCl.

Find the weight of 0.5 mole of O₂.

Find the number of molecules in 1.8 g of H₂O.

Find the number of moles in 10 g of CaCO₃.

Find the weight of 0.2 mole of H₂ gas.

Find the number of molecules in 3.2 g of SO₂.

Which of the following would weigh most?

Which of the following contains maximum number of molecules?

Calculate the number of particles in 0.1 mole of any substance.

Calculate the number of hydrogen atoms in 0.1 mole of H₂SO₄.

Calculate the number of molecules in one Kg of calcium chloride.

How many grams of Al are present in 0.2 mole of it?

How many grams of HCl are present in 0.1 mole of it?

How many grams of H₂O are present in 0.2 mole of it?

How many grams of CO₂ is present in 0.1 mole of it?

The mass of 5.6 litres of a certain gas at S.T.P. is 12 g. What is the relative molecular mass or molar mass of the gas?

Calculate the volume occupied at S.T.P. by 2 moles of SO₂.

Calculate the number of moles of CO₂ which contain 8.00 g of O₂

Calculate the number of moles of methane in 0.80 g of methane.

Calculate the weight/mass of an atom of oxygen.

Calculate the weight/mass of an atom of hydrogen.

Calculate the weight/mass of a molecule of NH₃.

Calculate the weight/mass of: `10^22` atoms of carbon

Calculate the weight/mass of the molecule of oxygen.

Calculate the weight/mass of 0.25 gram atom of calcium.

Calculate the mass of 0.1 mole of the following:

CaCO₃

(Ca = 40, Na = 23, Mg = 24, S = 32, C = 12, Cl = 35.5, O = 16, H = 1)

Calculate the mass of 0.1 mole of the following:

Na₂SO₄.10H₂O

(Ca = 40, Na = 23, Mg = 24, S = 32, C = 12, Cl = 35.5, O = 16, H = 1)

Calculate the mass of 0.1 mole of the following:

CaCl₂

(Ca = 40, Na=23, Mg =24, S=32, C = 12, Cl = 35.5, O=16, H=1)

Calculate the mass of 0.1 mole of the following:

Mg

(Ca = 40, Na = 23, Mg = 24, S = 32, C = 12, Cl = 35.5, O = 16, H = 1)

Calculate the number of oxygen atoms in 0.10 mole of Na₂CO₃.10H₂O.

Calculate the number of gram atoms in 4.6 gram of sodium.

Calculate the number of moles in 12g of oxygen gas.

What mass of Ca will contain the same number of atoms as are present in 3.2 g of S?

Calculate the number of atoms in the following: 

52 moles of He

Calculate the number of atoms in the following: 

52 amu of He

Calculate the number of atoms in the following: 

52 g of He

Calculate the number of atoms of each kind in 5.3 grams of sodium carbonate.

Calculate the mass of nitrogen supplied to soil by 5 kg of urea [CO(NH₂)₂].

[O = 16; N = 14; C = 12; H = 1]

Calculate the volume occupied by 320 g of sulphur dioxide at STP. [S = 32; O = 16]

What do you understand by the statement that 'vapour density of carbon dioxide is 22'?

The atomic mass of Chlorine is 35.5. What is its vapour density?

What is the mass of 56 cm³ of carbon monoxide at STP?

(C = 12 ,O = 16)

Determine the number of molecules in a drop of water which weighs 0.09 g.

The molecular formula for elemental sulphur is S₈. In a sample of 5.12 g of sulphur:

How many moles of sulphur are present?

The molecular formula for elemental sulphur is S₈.In a sample of 5.12 g of sulphur:

How many molecules and atoms are present?

If phosphorus is considered to contain P₄ molecules, then calculate the number of moles in 100g of phosphorus?

Calculate:

The gram molecular mass of chlorine if 308cm³ of it at STP weighs 0.979 g.

Calculate:

The volume of 4g of H₂ at 4 atmosphere.

Calculate:

The mass of oxygen in 2.2 litres of CO₂ at STP.

A student puts his signature with a graphite pencil. If the mass of carbon in the signature is 10^-12 g, calculate the number of carbon atoms in the signature.

An unknown gas shows a density of 3 g per litre at 273°C and 1140 mm Hg pressure. What is the gram molecular mass of this gas?

Cost of Sugar (C₁₂H₂₂ O₁₁) is Rs 40 per kg; calculate its cost per mole.

Which of the following weighs the least?

Four grams of caustic soda contains ______.

The number of molecules in 4.25 g of ammonia is ______.

Correct the statement, if required.

One mole of chlorine contains 6.023 x 10¹⁰ atoms of chlorine.

Correct the statement, if required.

Under similar conditions of temperature and pressure, two volumes of hydrogen combined with two volumes of oxygen will give two volumes of water vapour.

Correct the statement, if required.

The relative atomic mass of an element is the number of times one molecule of an element is heavier than `1/12` the mass of an atom of C¹².

Correct the statement, if required.

Under the same conditions of temperature and pressure, equal volumes of all gases contain the same number of atoms.

Give three kinds of information conveyed by the formula H₂O.

Explain the term empirical formula.

Give the empirical formula of C₆H₆.

Give the empirical formula of C₆H₁₈O₃

Give the empirical formula of C₂H₂

Give the empirical formula of CH₃COOH

Find the percentage of water of crystallisation in CuSO₄.5H₂O. (At. Mass Cu = 64, H = 1, O = 16, S = 32)

Calculate the percentage of phosphorus in Calcium hydrogen phosphate Ca(H₂PO₄)₂

Calculate the percentage of phosphorus in Calcium phosphate Ca₃(PO₄)₂

Calculate the percent composition of Potassium chlorate KClO₃.

Find the empirical formula of the compounds with the following percentage composition:

Pb = 62.5%, N = 8.5%, O = 29.0%

Calculate the mass of iron in 10 kg of iron ore which contains 80% of pure ferric oxide.

If the empirical formula of two compounds is CH and their vapour densities are 13 to 39 respectively, find their molecular formula.

Find the empirical formula of a compound containing 17.64% hydrogen and 82.35% of nitrogen.

On analysis, a substance was found to contain:

C = 54.54%, H = 9.09%, O = 36.36%

The vapour density of the substance is 44, calculate its empirical formula.

An organic compound, whose vapour density is 45, has the following percentage composition,

H = 2.22%, O = 71.19% and remaining carbon. Calculate its empirical formula.

An organic compound contains H = 4.07%, Cl = 71.65% chlorine and remaining carbon. Its molar mass = 98.96. Find its Empirical formula.

A hydrocarbon contains 4.8g of carbon per gram of hydrogen. Calculate the gram atom of each.

A hydrocarbon contains 4.8g of carbon per gram of hydrogen. Calculate:

find the empirical formula.

A hydrocarbon contains 4.8g of carbon per gram of hydrogen. Calculate Find molecular formula, if its vapour density is 29.

0.2 g atom of silicon combine with 21.3 g of chlorine. Find the empirical formula of the compound formed.

A gaseous hydrocarbon contains 82.76% of carbon. Given that its vapour density is 29, find its molecular formula.

In a compound of magnesium (Mg = 24) and nitrogen (N = 14), 18 g of magnesium combines with 7g of nitrogen.

Deduce the simplest formula by answering the following questions:

1. How many gram-atoms of magnesium are equal to 18g?
2. How many gram-atoms of nitrogen are equal to 7g of nitrogen?
3. Calculate the simple ratio of gram-atoms of magnesium to gram-atoms of nitrogen and hence the simplest formula of the compound formed.

Barium chloride crystals contain 14.8% water of crystallization. Find the number of molecules of water of crystallization per molecule.

Urea is a very important nitrogenous fertilizer. Its formula is CON₂H₄. Calculate the percentage of nitrogen in urea. (C = 12, O = 16, N = 14 and H = 1).

Determine the formula of the organic compound if its molecule contains 12 atoms of carbon. The percentage compositions of hydrogen and oxygen are 6.48 and 51.42 respectively.

A compound with empirical formula AB₂ has the vapour density equal to its empirical formula weight. Find its molecular formula.

A compound with empirical formula AB has vapour density 3 times its empirical formula weight. Find the molecular formula.

10.47 g of a compound contained 6.25 g of metal A and rest non-metal B. Calculate the empirical formula of the compound [At. wt of A = 207, B = 35.5]

A hydride of nitrogen contains 87.5% percent by mass of nitrogen. Determine the empirical formula of this compound.

A compound has O = 61.32%, S = 11.15%, H = 4.88% and Zn = 22.65%. The relative molecular mass of the compound is 287 amu. Find the molecular formula of the compound, assuming that all the hydrogen is present as a water of crystallization.

Complete the following blank in the equation as indicated.

\[\ce{CaH2_{(s)} + 2H2O_{( aq)}-> Ca(OH)2_{(s)} + 2H2_{(g)}}\]

Moles: 1 mole + ______ `→` ______ + ______

The reaction between 15 g of marble and nitric acid is given by the following equation:

\[\ce{CaCO3 + 2HNO3 -> Ca(NO3)2 + H2O + CO2}\]

Calculate the mass of anhydrous calcium nitrate formed.

The reaction between 15 g of marble and nitric acid is given by the following equation:

\[\ce{CaCO3 + 2HNO3 -> Ca(NO3)2 + H2O + CO2}\]

Calculate the volume of carbon dioxide evolved at S.T.P.

66g of ammonium sulphate is produced by the action of ammonia on sulphuric acid. Write a balanced equation and calculate mass of ammonia required.

The reaction between the red lead and hydrochloric acid is given below:

\[\ce{Pb3O4 + 8HCl -> 3PbCl2 + 4H2O + Cl2}\]

Calculate the mass of lead chloride formed by the action of the 6.85 g of red lead.

The reaction between the red lead and hydrochloric acid is given below:

\[\ce{Pb3O4 + 8HCl -> 3PbCl2 + 4H2O + Cl2}\]

Calculate the mass of the chlorine.

The reaction between the red lead and hydrochloric acid is given below:

\[\ce{Pb3O4 + 8HCl -> 3PbCl2 + 4H2O + Cl2}\]

Calculate the volume of the chlorine evolved at S.T.P.

Find the mass of KNO₃ required to produce 126 kg of nitric acid. Find whether a larger or smaller mass of NaNO₃ is required for the same purpose.

\[\ce{KNO3 + H2SO4 -> KHSO4 + HNO3}\]

\[\ce{NaNO3 + H2SO4 -> NaHSO4 + HNO3}\]

Pure calcium carbonate and dilute hydrochloric acid are reacted and 2 litres of carbon dioxide were collected at 27^oC and normal pressure.

\[\ce{CaCO3 + 2HCl -> CaCl2 + H2O + CO2}\]

Calculate the mass of salt required.

Calculate the mass and volume of oxygen at S.T.P., which will be evolved on electrolysis of 1 mole (18 g) of water.

1.56 g of sodium peroxide reacts with water according to the following equation:

\[\ce{2Na2O2 + 2H2O -> 4NaOH + O2}\]

Calculate the mass of sodium hydroxide formed.

Calculate the mass of ammonia that can be obtained from 21.4 g of NH₄Cl by the reaction:

\[\ce{2NH4Cl + Ca(OH)2 -> CaCl2 + 2H2O + 2NH3}\]

Aluminium carbide reacts with water according to the following equation.

\[\ce{Al4C3 + 12H2O -> 3CH4 + 4Al(OH)3}\]

What mass of aluminium hydroxide is formed from 12g of aluminium carbide?

\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]

0.02 moles of pure MnO₂ is heated strongly with conc. HCl. Calculate mass of MnO₂ used.

\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]

0.02 moles of pure MnO₂ is heated strongly with conc. HCl. Calculate moles of salt formed.

\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]

0.02 moles of pure MnO₂ is heated strongly with conc. HCl. Calculate the mass of salt formed.

\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]

0.02 moles of pure MnO₂ is heated strongly with conc. HCl. Calculate moles of chlorine gas formed.

\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]

0.02 moles of pure MnO₂ is heated strongly with conc. HCl. Calculate the mass of chlorine gas formed.

\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]

0.02 moles of pure MnO₂ is heated strongly with conc. HCl. Calculate the volume of chlorine gas formed at S.T.P.

\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]

0.02 moles of pure MnO₂ is heated strongly with conc. HCl. Calculate moles of acid required.

\[\ce{MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2}\]

0.02 moles of pure MnO₂ is heated strongly with conc. HCl. Calculate the mass of acid required.

Nitrogen and hydrogen react to form ammonia.

\[\ce{N2_{(g)} + 3H2_{(g)}-> 2NH3_{(g)}}\]

If 1000g H₂ reacts with 2000g of N₂

Will any of the two reactants remain unreacted? If yes, which one and what will be its mass?

From the equation for burning of hydrogen and oxygen

\[\ce{2H2 + O2 -> 2H2O}\] (Steam) 

Write down the number of mole (or moles) of steam obtained from 0.5 moles of oxygen.

From the equation

\[\ce{3Cu + 8HNO3 -> 3Cu(NO3)2 + 4H2O + 2NO}\]

(Atomic mass Cu = 64, H = 1, N = 14,O = 16)

Calculate the mass of copper needed to react with 63g of HNO₃.

Calculate the number of moles in 7g of nitrogen.

What is the volume at S.T.P. of 7.1 g of chlorine?

What is the mass of 56 cm³ of carbon monoxide at S.T.P?

Some of the fertilizers are sodium nitrate NaNO₃, ammonium sulphate (NH₄)₂SO₄ and urea CO(NH₂)₂. Which of these contains the highest percentage of nitrogen?

Water decomposes to O₂ and H₂ under suitable conditions as represented by the equation below:

\[\ce{2H2O -> 2H2 + O2}\]

If 2500 cm³ of H₂ is produced, what volume of O₂ is liberated at the same time and under the same conditions of temperature and pressure?

Urea [CO(NH₂)₂] is an important nitrogenous fertilizer. Urea is sold in 50 kg sacks. What mass of nitrogen is in one sack of urea?

Find the molecular formula of a hydrocarbon having vapour density 15, which contains 20% of Hydrogen.

The following experiment was performed in order to determine the formula of a hydrocarbon. The hydrocarbon X is purified by fractional distillation.

0.145 g of X was heated with dry copper (II) oxide and 224 cm³ of carbon dioxide was collected at S.T.P.

Which elements does X contain?

A compound is formed by 24 g of X and 64 g of oxygen. If the atomic mass of X = 12 and O = 16, calculate the simplest formula of the compound.

A gas cylinder filled with hydrogen holds 5 g of the gas. The same cylinder holds 85 g of gas X under the same temperature and pressure. Calculate the vapour density of gas X.

A gas cylinder filled with hydrogen holds 5g of the gas. The same cylinder holds 85 g of gas X under the same temperature and pressure. Calculate the molecular weight of gas X.

When carbon dioxide is passed over red hot carbon, carbon monoxide is produced according to the equation :

\[\ce{CO2 + C -> 2CO}\]

What volume of carbon monoxide at S.T.P. can be obtained from 3 g of carbon?

60 cm³ of oxygen was added to 24 cm³ of carbon monoxide and mixture ignited. Calculate the volume of oxygen used up.

How much calcium oxide is obtained by heating 82 g of calcium nitrate? Also, find the volume of NO₂ evolved:

\[\ce{2Ca(NO3)2 ->2CaO + 4NO2 + O2}\]

The equation for the burning of octane is:

\[\ce{2C8H18 + 25O2 -> 16CO2 + 18H2O}\]

How many moles of carbon dioxide are produced when one mole of octane burns?

The equation for the burning of octane is:

\[\ce{2C8H18 + 25O2 -> 16CO2 + 18H2O}\]

What volume, at STP, is occupied by 8 moles?

The equation for the burning of octane is:

\[\ce{2C6H18 + 25O2 -> 16CO2 + 18H2O}\]

If the relative molecular mass of carbon dioxide is 44, what is the mass of carbon dioxide produced by burning two moles of octane?

The equation for the burning of octane is:

\[\ce{2C8H18 + 25O2 -> 16CO2 + 18H2O}\]

What is the empirical formula of octane?

Ordinary chlorine gas has two isotopes \[\ce{^35_17Cl}\] and \[\ce{^37_17Cl}\] in the ratio of 3 : 1. Calculate the relative atomic mass of chlorine.

Silicon (Si = 28) forms a compound with chlorine (Cl = 35.5) in which 5.6 g of silicon combines with 21.3 g of chlorine. Calculate the empirical formula of the compound.

An acid of phosphorus has the following percentage composition; Phosphorus = 38.27%; hydrogen = 2.47%; oxygen = 59.26%. Find the empirical formula of the acid and its molecular formula, given that its relative molecular mass is 162.

Calculate the mass of substance 'A' which in gaseous form occupies 10 litres at 27°C and 700 mm pressure. The molecular mass of 'A' is 60.

A gas occupied 360 cm³ at 87°C and 380 mm Hg pressure. If the mass of gas is 0.546 g, find its relative molecular mass.

A gas cylinder can hold 1 kg of hydrogen at room temperature and pressure. What mass of carbon dioxide can it hold under similar conditions of temperature and pressure?

A gas cylinder can hold 1 kg of hydrogen at room temperature and pressure. If the number of molecules of hydrogen in the cylinder is X, calculate the number of carbon dioxide molecules in the cylinder. State the law that helped you to arrive at the result.

The following question refers to one mole of chlorine gas.

What is the volume occupied by this gas at STP?

The following question refers to one mole of chlorine gas.

What will happen to volume of gas, if pressure is doubled?

The following question refers to one mole of chlorine gas.

What volume will it occupy at 273°C?

The following question refers to one mole of chlorine gas.

If the relative atomic mass of chlorine is 35.5, what will be the mass of 1 mole of chlorine gas?

A hydrate of calcium sulphate CaSO₄.xH₂O contains 21% water of crystallization. Find the value of x.

What volume of hydrogen and oxygen measured at S.T.P. will be required to prepare 1.8 g of water?

How much volume will be occupied by 2 g of dry oxygen at 27°C and 740 mm pressure?

What would be the mass of CO₂ occupying a volume of 44 litres at 25°C and 750 mm pressure.

1 g of a mixture of sodium chloride and sodium nitrate is dissolved in water. On adding silver nitrate solution, 1.435 g of AgCl is precipitated.

\[\ce{AgNO3_{( aq)} + NaCl_{( aq)}-> AgCl_{(s)} + NaNO3}\]

Calculate the precentage of NaCl in the mixture.

From the equation:

\[\ce{C + 2H2SO4 -> CO2 + 2H2O + 2SO2}\]

Calculate the mass of carbon oxidized by 49 g of sulphuric acid (C = 12, relative molecular mass of sulphuric acid = 98)

From the equation:

\[\ce{C + 2H2SO4 -> CO2 + 2H2O + 2SO2}\]

Calculate the volume of sulphur dioxide measured at STP,  liberated at the same time.

A compound has the following percentage composition by mass: carbon 14.4%, hydrogen 1.2% and chlorine 84.5%. Determine the empirical formula of this compound. Work correctly to 1 decimal place. (H = 1; \[\ce{C}\] = 12; \[\ce{Cl}\] = 35.5)

A compound has the following percentage composition by mass: carbon 14.4%, hydrogen 1.2% and chlorine 84.5%. The relative molecular mass of this compound is 168, so what is its molecular formula?

Find the percentage of oxygen in magnesium nitrate crystals [Mg(NO₃).6H₂O].

Find the percentage of boron in Na₂B₄O₇.10H₂O. [H = 1, B = 11, O = 16, Na = 23].

Find the percentage of phosphorus in the fertilizer superphosphate Ca(H₂PO₄)₂.

What mass of copper hydroxide is precipitated by using 200 gm of sodium hydroxide?

\[\ce{2NaOH + CuSO4 -> Na2SO4 + Cu(OH)2↓}\]

[Cu = 64, Na = 23, S = 32, H = 1]

Solid ammonium dichromate decomposes as:

\[\ce{(NH4)2Cr2O7 -> N2 + Cr2O3 + 4H2O}\]

If 63 g of ammonium dichromate decomposes. Calculate the quantity in moles of (NH₄)₂Cr₂O₇.

Solid ammonium dichromate decomposes as:

\[\ce{(NH4)2Cr2O7 -> N2 + Cr2O3 + 4H2O}\]

If 63 g of ammonium dichromate decomposes. Calculate the quantity in moles of nitrogen formed.

Solid ammonium dichromate decomposes as:

\[\ce{(NH4)2Cr2O7 -> N2 + Cr2O3 + 4H2O}\]

If 63 g of ammonium dichromate decomposes. Calculate the volume of N₂ evolved at STP.

Solid ammonium dichromate decomposes as:

\[\ce{(NH4)2Cr2O7 -> N2 + Cr2O3 + 4H2O}\]

If 63 g of ammonium dichromate decomposes. Calculate what will be the loss of mass.

Solid ammonium dichromate decomposes as :

\[\ce{(NH4)2Cr2O7 -> N2 + Cr2O3 + 4H2O}\]

If 63 g of ammonium dichromate decomposes. Calculate calculate the mass of chromium (III) oxide formed at the same time.

Hydrogen sulphide gas burns in oxygen to yield 12.8 g of sulphur dioxide gas as under:

\[\ce{2H2S + 3O2 -> 2H2O + 2SO2}\]

Calculate the volume of hydrogen sulphide at STP. Also, calculate the volume of oxygen required at STP which will complete the combustion of hydrogen sulphide determined in litres.

Ammonia burns in oxygen and the combustion, in the presence of a catalyst, may be represented by;

\[\ce{2NH3 + 2 1/2O2 -> 2NO + 3H2O}\] [H = 1, N = 14, O = 16]

What mass of steam is produced when 1.5 g of nitrogen monoxide is formed?

If a crop of wheat removes 20 kg of nitrogen per hectare of soil, what mass of the fertilizer, calcium nitrate Ca(NO₃)₂ would be required to replace the nitrogen in a 10 hectare field?

Concentrated nitric acid oxidizes phosphorus to phosphoric acid according to the following equation:

\[\ce{P + 5HNO3 -> H3PO4 + 5NO2 + H2O}\]

If 6.2 g of phosphorus was used in the reaction, calculate the number of moles of phosphorus taken and mass of phosphoric acid formed.

Concentrated nitric acid oxidizes phosphorus to phosphoric acid according to the following equation:

\[\ce{P + 5HNO3 -> H3PO4 + 5NO2 + H2O}\]

If 6.2 g of phosphorus was used in the reaction, calculate the mass of nitric acid consumed at the same time.

Concentrated nitric acid oxidizes phosphorus to phosphoric acid according to the following equation:

\[\ce{P + 5HNO3 -> H3PO4 + 5NO2 + H2O}\]

If 6.2 g of phosphorus was used in the reaction, calculate the volume of steam produced at the same time if measured at 760 mm Hg pressure and 273°C.

112 cm³ of a gaseous fluoride of phosphorus has a mass of 0.63 g. Calculate the relative molecular mass of the fluoride. If the molecule of the fluoride contains only one atom of phosphorus, then determine the formula of the phosphorus fluoride. [ F = 19, P = 31].

Washing soda has formula Na₂CO₃.10H₂O. What mass of anhydrous sodium carbonate is left when all the water of crystallization is expelled by heating 57.2 g of washing soda?

A metal M forms a volatile chloride containing 65.5% chlorine. If the density of the chloride relative to hydrogen is 162.5, find the molecular formula of the chloride (M = 56).

A compound X consists of 4.8% carbon and 95.2% bromine by mass. Determine the empirical formula of this compound working correctly to one decimal place (C = 12; Br = 80).

A compound X consists of 4.8% carbon and 95.2% bromine by mass. If the vapour density of the compound is 252, what is the molecular formula of the compound?

The reaction: \[\ce{4N2O + CH4 -> CO2 + 2H2O + 4N2}\] takes place in the gaseous state. If all volumes are measured at the same temperature and pressure, calculate the volume of dinitrogen oxide (N₂O) required to give 150 cm³ of steam.

Samples of the gases O₂, N₂, CO₂ and CO under the same conditions of temperature and pressure contain the same number of molecules x. The molecules of oxygen occupy V litres and have a mass of 8 g under the same conditions of temperature and pressure.

What is the volume occupied by:

1. x molecules of N₂,
2. 3x molecules of CO,
3. What is the mass of CO₂ in grams?
4. In answering the above questions, which law have you used?

The percentage composition of sodium phosphate as determined by analysis is 42.1% sodium, 18.9% phosphorus and 39% oxygen. Find the empirical formula of the compound.

What volume of oxygen is required to burn completely a mixture of 22.4 dm³ of methane and 11.2 dm³ of hydrogen into carbon dioxide and steam?

\[\ce{CH4 + 2O2 -> CO2 + 2H2O}\]

\[\ce{2H2 + O2 -> 2H2O}\]

The gases hydrogen, oxygen, carbon dioxide, sulphur dioxide, and chlorine are arranged in order of their increasing relative molecular masses. Given 8 g of each gas at STP, which gas will contain the least number of molecules and which gas the most?

10 g of a mixture of sodium chloride and anhydrous sodium sulphate is dissolved in water. An excess of barium chloride solution is added and 6.99 g of barium sulphate is precipitated according to the equation given below:

\[\ce{Na2SO4 + BaCl2 -> BaSO4 + 2NaCl}\]

Calculate the percentage of sodium sulphate in the original mixture.

When heated, potassium permanganate decomposes according to the following equation :

\[\ce{2KMnO4 -> \underset{\text{solid residue}}{K2MnO4 + MnO2} + O2}\]

(a) Some potassium permanganate was heated in the test tube. After collecting one litre of oxygen at room temperature, it was found that the test tube had undergone a loss in mass of 1.32 g. If one litre of hydrogen under the same conditions of temperature and pressure has a mass of 0.0825 g, calculate the relative molecular mass of oxygen.

(b) Given that the molecular mass of potassium permanganate is 158. What volume of oxygen (measured at room temperature) would be obtained by the complete decomposition of 15.8 g of potassium permanganate? (Molar volume at room temperature is 24 litres)

A flask contains 3.2 g of sulphur dioxide. Calculate the following:

1. The moles of sulphur dioxide present in the flask.
2. The number of molecules of sulphur dioxide present in the flask.
3. The volume occupied by 3.2 g of sulphur dioxide at STP

(S = 32, O = 16)

An experiment showed that in a lead chloride solution, 6.21 g of lead is combined with 4.26 g of chlorine. What is the empirical formula of this chlorine? (Pb = 207; Cl = 35.5)

The volumes of gases A, B, C and D are in the ratio, 1 : 2 : 2 : 4 under the same conditions of temperature and pressure.

1. Which sample of gas contains the maximum number of molecules?
2. If the temperature and pressure of gas A are kept constant, then what will happen to the volume of A when the number of molecules is doubled?
3. If this ratio of gas volume refers to the reactants and products of a reaction, which gas law is being observed?
4. If the volume of A is actually 5.6 dm³ at STP, calculate the number of molecules in the actual Volume of D at STP (Avogadro's number is 6 × 10²³).
5. Using your answer from (iv), state the mass of D if the gas is dinitrogen oxide (N₂O).

The equation given below relates the manufacture of sodium carbonate (molecular weight of Na₂CO₃ = 106).

1. NaCl+NH₃+ CO₂+ H₂O→ NaHCO₃+NH₄Cl
2. 2NaHCO₃→ Na₂CO₃+H₂O + CO₂

Equations (1) and (2) are based on the production of 21.2 g of sodium carbonate.

(a) What mass of sodium hydrogen carbonate must be heated to give 21.2 g of sodium carbonate?

(b) To produce the mass of sodium hydrogen carbonate calculate in (a), what volume of carbon dioxide, measured at S.T.P. would be required?

A sample of ammonium nitrate when heated yields 8.96 litres of steam (measure at STP).

\[\ce{NH4NO3 -> N2O + 2H2O}\]

1. What volume of dinitrogen oxide is produced at the same time as 8.96 litres of steam?
2. What mass of ammonium nitrate should be heated to produce 8.96 litres of steam? (Relative molecular mass of ammonium nitrate is 80).
3. Determine the percentage of oxygen in ammonium nitrate (O = 16).

Given that the relative molecular mass of copper oxide is 80, what volume of ammonia (measured at STP) is required to completely reduce 120g of copper oxide? The equation for the reaction is:

\[\ce{3CuO + 2NH3 → 3Cu + 3H2O + N2}\]

Calculate the number of moles and number of molecules present in 1.4 g of ethylene gas. What is the volume occupied by the same amount of ethylene?

What is the vapour density of ethylene? (Avogadro's number = 6 x 10²³; Atomic weight of C = 12, H = 1; Molar volume = 22.4 litres at STP)

Calculate the percentage of sodium in sodium aluminium fluoride (Na₃AlF₆) correct to the nearest whole number. (F = 19; Na = 23; Al = 27)

560 ml of carbon monoxide is mixed with 500 ml of oxygen and ignited. The chemical equation for the reaction is as follows:

\[\ce{2CO + O2 -> 2CO2}\]

Calculate the volume of oxygen used and carbon dioxide formed in the above reaction.