Page 2 - 2. PRACTICE WORKSHEET

DIRECTION:Each of these questions contains an Assertion followed by Reason. Read them
carefully and answer the question on the basis of following options. You have to select the one
that best describes the two statements.
(a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion.
(c) If Assertion is correct but Reason is incorrect.

(d) If Assertion is incorrect but Reason is correct.
(e) If Assertion & Reason both are incorrect.
Q.5Assertion: When 10g of CaCO3 is decomposed,5.6g of residue is left and 4.4g of
CO2 escapes.

Reason: Law of conservation of mass is followed.
Q.6 Assertion: Pure water obtained from different sources such as river, well, spring,
sea etc. always contains hydrogen and oxygen combined in the ratio of 1:8 by mass.
Reason: A chemical compound always contains same elements combined in same
fixed proportion by mass.
Q.7Hydrogen and oxygen combine inthe ratio of 1:8 by mass to form water. What

mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Q.8A 0.24 g sample of compound of oxygen and boron was found by analysis to

contain 0.096 g of boron and 0.144 g of oxygen.Calculate the percentage

composition of the compound byweight.
Q.9Which postulates of Dalton’s atomic theory tells us about the laws of chemical

combinations?

Q.10 The percentage of three elements calcium, carbon and oxygen in a sample of
calcium carbonate is given as: Calcium =40%; Carbon =12.0%; Oxygen = 48%. If the
law of constant proportion is true, what weights of these elements will be present in
1.5 g of another sample of calcium carbonate?

(Atomic mass of Ca = 40 u, C = 12 u, O = 16 u)