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प्रश्न
Which changes occur during chemical changes?
उत्तर
The chemical composition of substance changes during chemical changes i.e., new substances are formed.
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संबंधित प्रश्न
A solution of a substance ‘X’ is used for white washing.
- Name the substance ‘X’ and write its formula.
- Write the reaction of the substance ‘X’ named in (i) above with water.
Why is respiration considered an exothermic reaction? Explain.
One of the following is an endothermic reaction. This is:
(a) combination of carbon and oxygen to form carbon monoxide
(b) combination of nitrogen and oxygen to form nitrogen monoxide
(c) combination of glucose and oxygen to form carbon dioxide and water
(d) combination of zinc and hydrochloric acid to form zinc chloride and hydrogen
Gas A, which is the major cause of global warming, combines with hydrogen oxide B in nature in the presence of an environmental factor C and a green material D to form a six carbon organic compounds E and a gas F. The gas F is necessary for breathing.
(a) What is gas A?
(b) What is the common name of B?
(c) What do you think could be C?
(d) What is material D? Where is it found?
(e) Name the organic compound E.
(f) What is gas F? Name the natural process during which it is released.
What type of reaction is represented by the following equation?
2 Ca + O2 → 2CaO
What type of chemical reaction take place when a magnesium wire is burnt in air?
What type of chemical reaction is represented by the following equation?
A + B → C
what tpye of reaction is the following:
2K + Cl → 2KCl
Give one example of a combination reaction which is also endothermic.
Consider the following equation of the chemical reaction of a metal M:
4M + 3O2 → 2M2O3
This equation represents:
(a) combination reaction as well as reduction reaction
(b) decomposition reaction as well as oxidation reaction
(c) oxidation reaction as well as displacement reaction
(d) combination reaction as well as oxidation reaction
Define a chemical reaction.
Give one example each of which illustrates the following characteristics of a chemical reaction:
change of colour
Classify the following reaction as combination, decomposition, displacement, precipitation and neutralization. Also balance the equation.
\[\ce{CaCO3_{(s)} ->[heat]CaO_{(s)} + CO2_{(g)}}\]
Explain the following type of chemical reaction, giving two examples for it:
Combination reaction
Explain the terms with examples.
Combination reaction
Define: Chemical combination reaction
Calcium oxide reacts vigorously with water to produce slaked lime.
\[\ce{CaO{(s)} + H2O(l) -> Ca(OH)2(aq)}\]
This reaction can be classified as:
(A) Combination reaction
(B) Exothermic reaction
(C) Endothermic reaction
(D) Oxidation reaction
Classify the following reaction into different type:
CaO(s) + H2O(l) → Ca(OH)2(aq)
Give a balanced equation for –
A direct combination reaction involving two elements, one of which is a non-metal
H2(g) + Cl29(g) → 2HCl(g) is a ______
Combustion reactions are always ____________.
In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?
The respiration process during which glucose undergoes slow combustion by combining with oxygen in the cells of our body to produce energy is a kind of:
The Salt Story
From: The New Indian Express 9 March 2021
The salt pans in Marakkanam, a port town about 120 km from Chennai are the third largest producer of salt in Tamil Nadu. Separation of salt from water is a laborious process and the salt obtained is used as raw materials for manufacture of various sodium compounds.
One such compound is Sodium hydrogen carbonate, used in baking, as an antacid and in soda acid fire extinguishers.
The table shows the mass of various compounds obtained when 1litre of sea water is evaporated.
| COMPOUND | FORMULA | MASS OF SOLID PRESENT /g |
| Sodium Chloride | NaCl | 28.0 |
| Magnesium Chloride | MgCl2 | 8.0 |
| Magnesium Sulphate | MgSO4 | 6.0 |
| Calcium Sulphate | CaSO4 | 2.0 |
| Calcium Carbonate | CaCO3 | 1.0 |
| TOTAL AMOUNT OF SALT OBTAINED | 45.0 | |
Which compound in the table reacts with acids to release carbon dioxide?
Balance the following chemical equation and identify the type of chemical reaction.
`"Mg"("s") + "Cl"_2("g") -> "MgCl"_2("s")`
Balance the following chemical equation and identify the type of chemical reaction.
`"CaO"("s") + "SiO"_2("s") -> "CaSio"_3("s")`
Give the chemical reaction when a few pieces of slaked lime are added to a beaker half-filled with water. Will it be an endothermic or exothermic reaction?
Read the text below and answer the questions that follow:
A small amount of hydrochloric acid was taken in a test tube. The test tube was heated. A glass rod was dipped in the ammonia solution and held on the top of the test tube. A white smoke was seen emanating from the tip of the glass rod.
- What must have happened?
- Which colour of gas is formed?
- Write the chemical equation for the reaction.
