Question

Q5 Multiple Choice Questions : -

(i) Name and state the law which is kept in mind while we balance a chemical equation.

(a) Law of Equal Proportion (b) Law of Conservation of Mass

(c) Daltons Law (d) Avogadro’s Law

(ii) What is breaking and making of bonds in chemical reaction called?

(a) Chemical Reaction (b) Chemical Equation

(c) Chemical Bonding (d) Chemical Equilibrium

(iii) What are the coefficients of the correctly balanced equation?

?Fe2O3 + ?CO → ?Fe+ ?CO2

(a) 0, 2, 2,3 (b) 1,3,2,3 (c) 1,2,2,2 (d) 2,6, 4,3

(iv) Three beakers labelled as A, B and C each containing 25 ml of water were taken. A small amount of NaOH,

anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was

an increase in the temperature of the solution contained in beakers A and B, whereas in case of beaker C, the

temperature of the solution falls. Which one of the following statement(s) is (are) correct?

(i) In beakers A and B, exothermic process has occurred.

(ii) In beakers A and B, endothermic process has occurred.

(iii) In beaker C exothermic process has occurred.

(iv) In beaker C endothermic process has occurred.

(a) (i) only (b) (ii) only (c) (i) and (iv) (d) (iv), (ii) and (iii)

(v) Before burning in air, the magnesium ribbon is cleaned by rubbing with a sand paper to :

(a) Make the ribbon surface shinier

(b) Remove the layer of magnesium oxide from the ribbon surface

(c) Remove the layer of magnesium carbonate from the ribbon surface

(d) Remove the moisture from the ribbon surface

Q6 Give reasons : -

(i) All decomposition reactions are endothermic reactions.

(ii) Photosynthesis is considered as an endothermic reaction.

(iii) An iron knife kept dipped in a blue copper sulphate solution turns the blue solution light green.

(iv) When carbon dioxide is passed through lime water, it turns milky.

(v) Hydrogen being a highly inflammable gas and oxygen being a supporter of combustion, yet water which is a

compound made up of hydrogen and oxygen is used to extinguish fire.​

Answer 1

Answer:

1. law of conservation of mass

2. chemical equation

3.2,6,4,3

4.only c

5. remove the layer of magnesium oxide