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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.
Find the odd man out:
Camphor, Ammonium Chloride, Naphthalene balls, Sugar
A silvery-white metal X taken in the form of ribbon, when ignited, burns in air with a dazzling white flame to form a white powder Y. When water is added to powder Y, it dissolves partially to form another substance Z.
(a) What could metal X be?
(b) What is powder Y?
(c) With which substance metal X combines to form powder Y?
(d) What is substance Z? Name one domestic use of substance Z.
(e) Write a balanced chemical equation of the reaction which takes place when metal X burns in air to form powder Y.
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 tpye of reaction is the following:
2K + Cl → 2KCl
Define a combination reaction.
When hydrogen burns in oxygen, water is formed and when water is electrolysed, then hydrogen and oxygen are produced. What type of reaction takes place:
(a) in the first case?
(b) in the second case
Define a chemical reaction.
What happens during a chemical reaction ?
Give one example each of which illustrates the following characteristics of a chemical reaction:
change of colour
Fill in the blank
A reaction in which two or more substances combine to form a single substance is called a ............ reaction.
A student prepared an aqueous solution of CuSO4 in beaker X and an aqueous solution of FeSO4 in beaker Y. He then dropped some iron pieces in beaker X and some zinc pieces in beaker Y. After about 10 hours he observed that the solutions in X and Y respectively appear:
(A) blue and green
(B) colourless and pale green
(C) colourless and light blue
(D) greenish and colourless
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
State why a direct combination reaction is called a – ‘synthesis reaction’.
Select the correct answer for the statement given below:
The product formed during direct combination reaction of carbon dioxide and water.
H2(g) + Cl29(g) → 2HCl(g) is a ______
Define a combination reaction. Give one example of an exothermic combination reaction.
Which of the following are exothermic processes?
(i) Reaction of water with quick lime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor (crystals)
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 chemical reaction between copper and oxygen can be categorized as ______.
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?
Identify the correct option from the given table which represents the type of reactions occurring in step 1 and step 2.
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.
`"Na"("s") + "S"("s") overset("(Fuse)")(->) "Na"_2"S"("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?
A clear solution of slaked lime is made by dissolving Ca(OH)2 in an excess of water. This solution is left exposed to air. The solution slowly goes milky as a faint white precipitate forms. Explain why a faint white precipitate forms, support your response with the help of a chemical equation.
A metal ribbon 'X' bums in oxygen with a dazzling white flame forming a white ash 'Y'. The correct description of X, Y and the type of reaction is:
- Assertion: Rusting of Iron is endothermic in nature.
- Reason: As the reaction is slow, the release of heat is barely evident.
