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ICSE Class 10 Chemistry Question 8 of 23

Solved Sample Paper 1 — Question 15

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15
Question

Question 1(xv)

The atomic masses of nitrogen (N), oxygen (O) and neon (Ne) are approximately 14, 16 and 20.18 respectively.

Which of the following statements regarding the number of atoms in 14 g of nitrogen, 16 g of oxygen and 20 g of neon is correct?

P. 14 g of nitrogen contains double number of atoms as 20 g of neon.

Q. 16 g of oxygen contains two times the number of atoms as 14 g of nitrogen.

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

Neither P nor Q

Reason — According to Avogadro's number (NA) = 6.022 x 1023 atoms are present in one mole of element.

In case of P,

Number of atoms in 14 g of N

= Given massAtomic mass\dfrac{\text{Given mass}}{\text{Atomic mass}} x NA

= 1414\dfrac{14}{14} X 6.022 x 1023

= 6.022 x 1023

Number of atoms in 20 g of Ne

= Given massAtomic mass\dfrac{\text{Given mass}}{\text{Atomic mass}} x NA

= 2020.18\dfrac{20}{20.18} X 6.022 x 1023

= 0.99 x 6.022 x 1023

= 5.96 x 1023 atoms

As number of atoms in 14 g of nitrogen is almost equal to 20 g of Neon. Hence, statement P is incorrect.

In case of statement Q,

Number of atoms in 16 g of oxygen

= Given massAtomic mass mass\dfrac{\text{Given mass}}{\text{Atomic mass mass}} X NA

= 1616\dfrac{16}{16} X 6.022 x 1023

= 6.022 x 1023

As number of atoms in 16 g of oxygen is equal to 14 g of nitrogen. Hence, statement Q is also incorrect.