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Quetion 1. In a reaction, 5.3 g of sodium
carbonate reacted with 6 g of
ethanoic acid. The products were
2.2 g of carbon =
dioxide, 0.9 g
water and 8.2 g of sodium
ethanoate. Show that theseobservations are in agreement
with the law of conservation of
mass.
sodium carbonate + ethanoic acid
→ sodium ethanoate + carbon
dioxide + water
Quetion 2. Hydrogen and oxygen combine in
the 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?
Quetion 3. Which postulate of Dalton’s
atomic theory is the result of the
law of conservation of mass?
Quetion 4. Which postulate of Dalton’s
atomic theory can explain the law
of definite proportions?
Quetion 1. Define the atomic mass unit.
Quetion 2. Why is it not possible to see an
atom with naked eyes?
Quetion 1.Following formulae:
(i) Al2(SO4)3
(ii) CaCl2
(iii) K2SO4
(iv) KNO3
(v) CaCO3.
Question 2. What is meant by the term
chemical formula?
Question 3. How many atoms are present in a
(i) H2S molecule and
(ii) PO4
3– ion?
Question 1. Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium suphide
(iv) magnesium hydroxide
Question 2. Write down the names of
compounds represented by the
Question 2. Calculate the molecular masses
of H2, O2, Cl2, CO2, CH4, C2H6,
C2H4, NH3, CH3OH.
Question 2. Calculate the formula unit
masses of ZnO, Na2O, K2CO3,
given atomic masses of Zn = 65 u,
Na = 23 u, K = 39 u, C = 12 u,
and O = 16 u.
Question 1. If one mole of carbon atoms
weighs 12 gram, what is the
mass (in gram) of 1 atom of
carbon?
Question 2. Which has more number of
atoms, 100 grams of sodium or
100 grams of iron (given, atomic
mass of Na = 23 u, Fe = 56 u)?
Question 1. A 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 by
weight.
Question 2. When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of
carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen?
Which law of chemical combination will govern your answer?
Question 3. What are polyatomic ions? Give examples.
Question 4. Write the chemical formulae of the following.
(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate
(d) Aluminium chloride
(e) Calcium carbonate.
Question 5. Give the names of the elements present in the following
compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Question 6. Calculate the molar mass of the following substances.
(a) Ethyne, C2H2
(b) Sulphur molecule, S8
(c) Phosphorus molecule, P4 (Atomic mass of phosphorus
= 31)
(d) Hydrochloric acid, HCl
(e) Nitric acid, HN
O3
Question 7. What is the mass of—
(a) 1 mole of nitrogen atoms?
(b) 4 moles of aluminium atoms (Atomic mass of aluminium
= 27)?
(c) 10 moles of sodium sulphite (Na2SO3)?
Question 8. Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.
Question 9. What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
Question 10. Calculate the number of molecules of sulphur (S8) present in
16 g of solid sulphur.
Question 11. Calculate the number of aluminium ions present in 0.051 g of
aluminium oxide.
(Hint: The mass of an ion is the same as that of an atom of the
same element. Atomic mass of Al = 27 u)
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