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ICSE Class 10 Chemistry Question 4 of 23

Solved Sample Paper 3 — Question 15

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15
Question

Question 1(xv)

The molecular mass of CO2 and O2 are approximately 44 and 32 respectively. Which of the following statements regarding the mass of oxygen and number of molecules of oxygen is correct?

P. The mass of oxygen in 2.24 litres of CO2 is 3.2 g

Q. The number of molecules of oxygen present in it is 6.022 x 1023

  1. Only P
  2. Only Q
  3. Both P and Q
  4. Neither P nor Q
Answer

Only P

Reason —

P: As 22.4 L of CO2 at S.T.P. has mass = 44 g

Therefore, 2.24 L of CO2 at S.T.P. has mass = 4422.4\dfrac{44}{22.4} x 2.24 = 4.4 g

44 g of CO2 has 32 g of oxygen

So, 4.4 g of CO2 will have = 3244\dfrac{32}{44} x 4.4 = 3.2 g of oxygen.

Hence P is correct.

Q: No. of moles of O2 in 3.2 g = 3.232\dfrac{3.2}{32} = 0.1 g .

1 mole of O2 = 6.023 x 1023 molecules

0.1 moles has molecules = 6.023 x 1023 x 0.1 = 6.023 x 1022

Hence Q is incorrect.