1. Fill in the blanks
(a) In a chemical reaction, the sum of the masses of the reactants and
products remains unchanged. This is called ————.
(b) A group of atoms carrying a fixed charge on them is called ————.
(c) The formula unit mass of Ca3 (PO4)2
is --------------------
(d) Formula of sodium carbonate is ———— and that of ammonium sulphate is
——
2. Compute the difference in masses of 103 moles each of
magnesium atoms and magnesium ions.
(Mass of an electron = 9.1×10–31 kg)
4. Compute the number of ions present in 5.85 g of sodium chloride.
5. A gold sample contains 90% of gold and the rest copper. How many
atoms of gold are present in one gram of this sample of gold?
6. What are ionic and molecular compounds? Give examples.
7. Compute the difference in masses of one mole each of aluminum atoms
and one mole of its ions. (Mass of an electron is (9.1×10–28 g). which one is heavier?
8. A silver
ornament of mass ‘m’ gram is polished with gold equivalent to 1% of the mass of
silver. Compute the ratio of the number of atoms of gold and silver in the
ornament.
9. A sample
of ethane (C2H6) gas has the same mass as 1.5 ×1020
11. Does
the solubility of a substance change with temperature? Explain with the help of
an example.
12.
Calculate the number of moles of magnesium present in a magnesium ribbon
weighing 12 g. Molar atomic mass of magnesium is 24g mol-1
13. Verify
by calculating that
(a) 5 moles
of CO2 and 5 moles of H2O do not have the same mass.
(b) 240 g
of calcium and 240 g magnesium elements have a mole ratio of 3:5.
14. A
sample of vitamin C is known to contain 2.58 ×1024 oxygen atoms. How many moles of
oxygen atoms are present in the sample?
15. The
visible universe is estimated to contain 1022 stars. How many moles of stars
are present in the visible universe?
16. Compare
the properties of electrons, protons and neutrons.
17. What
are the limitations of J.J. Thomson’s model of the atom?
18. What
are the limitations of Rutherford’s model of atom?
19.
Describe Bohr’s model of atom.
20. Compare
all the proposed models of an atom given in this chapter.
21.
Summarize the rules for writing of distribution of electrons in various shells
for the first eighteen elements.
22. Define
valency by taking examples of silicon and oxygen
23. Explain
with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and (iv)
Isobars. Give any two uses of isotopes.
24. Na+ has
completely filled K and L shells. Explain.
25. If
bromine atom is available in the form of, say, two isotopes 7935Br (49.7%)
and 8135Br
(50.3%), calculate the average
atomic mass of bromine atom.
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Numerical based on mole concept Related post to 9th Atoms and Molecules
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