Questions
22
Naturally occurring thallium consists of two stable isotopes, Tl-203 and Tl-205 (atomic mass = 203.0 and 205.0, respectively) and has an average atomic mass of 204.4. What is percentage of Tl – 205?
Answer: 70.0%
23
Total mass of 1 mole of CO2 + 10 g mole of O2 + 5 g molecule of SO3 + 5 g atom of Na + 10 g of SO3 + 5 g of Na atom
Answer: 894 g
24
Four containers of 2 L capacity contains dinitrogen as described below. Which one contains maximum number of molecules?
Answer: 82 g of dinitrogen
25
Which of the following represents 1 g mole of the substance
Answer: 4 g of He
28
The number of moles of oxygen in 1 L of air containing 21% oxygen by volume, in standard conditions, is
Answer: 0.0093 mol
29
4 g of an unknown gas occupies 2.24 L of volume at Standard temperature and pressure. The gas may be
Answer: Carbon dioxide
30
In a mole of water vapours at STP, the volume actually occupied or taken by the molecules (i.e., Avogadro’s No. x volume of one molecule) is
Answer: 1% to 2% of 22.4 L
32
32 g O2, 2 g H2 and 28 g N2 at STP occupy separately a volume of
Answer: 22.4 L
33
Which of the following contains maximum number of molecules?
Answer: 50 cc of SO2 at STP
35
An alkaloid contains 17.28% of nitrogen and its molecular mass is 162. The number of nitrogen atoms present in one molecule of alkaloid is:
Answer: Two
36
How many atoms are contained in one mole of sucrose (C12H22OH)?
Answer: 45 6.02 1023 atoms/mole
40
0.2 mole of HCl and 0.2 mole of barium chloride were dissolved in water to produce a 500 mL solution. The molarity of the Cl– ions is:
Answer: 1.2 M
