Question

One mole of oxygen gas at STP is equal to :

(i) 6.022 × 10²³ molecules of oxygen

(ii) 6.022 × 10²³ atoms of oxygen

(iii) 16 g of oxygen

(iv) 32 g of oxygen

Answer 1

(i) 6.022 × 10²³ molecules of oxygen

(iv) 32 g of oxygen

Explanation:

One mole of oxygen gas at STP is equal to 6.022 × 1023 molecules of oxygen.

The number of moles is given by the following formula,

Moles = `"Mass"/"Molar mass"`  ......(1)

The number of moles of \[\ce{O2}\] is calculated by using equation (1) as follow.

Moles of O₂ = `(16 g)/((32 g)/(mol)` = 0.5 mol

The number of molecules can be calculated as, number of moles = `"Number of molecules"/"Avogadro's number"`  ......(2)

On substituting the values in the above equation:

0.5 mil = `"Number of molecules"/(6.022 xx 10^23)`

Number of molecules = 0.5 × 6.022 × 10²³

The number of moles is given by the following formula,

Moles = `"Mass"/"Molar mass"`  ......(1)

The number of moles of \[\ce{O2}\] is calculated by using equation (1) as follows,

Moles of \[\ce{O2}\] = `(32 g)/((32 g)/(mol)` = 1 mol

The number of molecules can be calculated as, number of moles = `"Number of molecules"/"Avogadro's number"`  ......(2)

On substituting the values in the above equation:

1 mol = `"Number of molecules"/(6.022 xx 10^23)`

Number of molecules = 1 × 6.022 × 10²³