Question

8 Which gas sample contains the smallest number of molecules?
A 4g of helium
B 16g of oxygen
C 28g of carbon monoxide
D 28g of nitrogen​

Answer 1

Answer:

B

Explanation:

Oxygyen = O2

O2 = 16x2

= 32

Moles = mass/Mr

16/32 = 0.5

Answer 2

The correct option regarding the number of molecules is lowest for B 16g of oxygen.

Given:

A gas sample contains 4g of helium, 16g of oxygen, 28g of carbon monoxide, and 28g of nitrogen.

To Find:

The number of molecules.

Solution:

To find the number of molecules we will follow the following steps:

As we know,

The molecular mass of Helium, oxygen, carbon monoxide, and nitrogen is 4,32,28, and 28g/mol.

Now,

The number of molecules is calculated by multiplying the total moles and Avogardro number(Na).

$Na = 6.022 \times {10}^{23}$

Molecules = moles × Avogadro number

So,

A compound with the smallest moles will have the smallest number of molecules.

Number of moles =

$\frac{given \: mass}{molecular \: mass}$

Now,

Number of moles of Helium =

$\frac{4}{4} = 1$

Number of moles of oxygen =

$\frac{16}{32} = 0.5$

Number of moles of carbon monoxide =

$\frac{28}{28} = 1$

Number of moles of nitrogen =

$\frac{28}{28} = 1$

Henceforth, the correct option regarding the number of molecules is lowest for B 16g of oxygen.

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