Appearances are deceptive

Appearances are deceptive

CBSE X Chemical Reaction and Equation Extra marks questions answers

 1-mark Questions/ Answers
1. What happens when magnesium ribbon burns in air?
Ans. When magnesium ribbon burns in air, it combines with the oxygen to form magnesium oxide.
 2Mg(s) + O2(g)  2MgO(s)

2. Name the gas evolved when zinc reacts with dil. HCl.
Ans. Hydrogen gas is evolved.

3. What is a chemical equation?
Ans. A chemical equation is a symbolic notation that uses formulae instead of words to represent a chemical equation.

4. On what chemical law, balancing of chemical equation is based?
Ans. Balancing of a chemical equation is based on the law of conservation of mass.

5. Represent decomposition of ferrous sulphate with the help of balanced chemical equation.
Ans. 2FeSO4(s)  Fe2O3(s) + SO2 (g) + SO3 (g)

6. When carbon dioxide is passed through lime water, it turns milky, why?
Ans. Lime water (calcium hydroxide) combines with carbon dioxide to form a suspension of calcium carbonate which makes lime water milky. Ca (OH) 2 + CO2  CaCO3 + H2O

7. A zinc rod is left for nearly 20 minutes in a copper sulphate solution. What change would you observe in zinc rod?               
Ans. Zinc rod will change into zinc sulphate.

8. What type of reaction is this:  Na2SO4           +          BaCl2            BaSO4 +          2NaCl.
Ans. It is a double displacement reaction.

9. Identify the compound oxidized in the following reaction. H2S (g) + Cl2   S(s) + 2HCl (g).
Ans. H2S is oxidized.

10. How does the food become rancid?
Ans. Food becomes rancid when fat and oils present in the food are oxidized.

2-marks Questions/ Answers
Q.1. An iron knife kept dipped in a blue copper sulphate solution turns the blue solution light green. Why?
Ans. As we know iron is more reactive than copper. So, it displaces Cu from CuSO4 solution and forms ferrous sulphate which is of Light Green Colour.
CuSO4 (aq) + Fe (s)      →        FeSO4 (aq)                  +...

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