Chapter U3, Problem 9RE

(a)

Interpretation Introduction

Interpretation :

22.4 L N₂ is given at STP. The temperature and pressure of the sample must be found out.

Concept Introduction :

STP stands for standard temperature and pressure.

Answer to Problem 9RE

Temperature and pressure of the nitrogen sample is 273 K and 1 atm respectively.

Explanation of Solution

22.4 L N₂ gas is given at STP. As the gas is in standard condition so it will have standard temperature which is 0°C. In absolute scale it will be $\text{(0+273)K=273K}$ .

Standard pressure is equal to 1 atm.

b)

Interpretation Introduction

Interpretation :

Number of molecules in 22.4 L of N₂at STP must be found out.

Concept Introduction :

At STP 1 mol of any gas occupies 22.4 L.

Answer to Problem 9RE

Number of molecules in 22.4 L of N₂ gas is $6.023\times {10}^{23}$ .

Explanation of Solution

22.4 L gas at STP is 1 mol. 1 mol gas must contain Avogadro’s number of molecules.

Thus 22.4 L N₂ gas must contain $6.023\times {10}^{23}$ number of molecules.

c)

Interpretation Introduction

Interpretation :

Number of atoms in 22.4 L of N₂ at STP must be found.

Concept Introduction :

Number of molecules per mol of substance is equal to Avogadro’s number which is equal to $6.023\times {10}^{23}$ .

Atomicity is the number of atoms per molecules of an element.

Number of atoms $\text{=atomicity×number of molecules}$

Answer to Problem 9RE

N₂ has $\text{1}\text{.20}\times {\text{10}}^{24}$ number of N atoms.

Explanation of Solution

At STP 22.4 L N₂ gas is equal to 1 mol.

Number of molecules in each gas sample is $6.023\times {10}^{23}$ .

N_2has 2 atoms per molecule.

Number of atoms of N₂$\text{=2}\times \text{6}\text{.023}\times {\text{10}}^{\text{23}}\text{.}$

  $\text{=1}\text{.20}\times {\text{10}}^{24}$ .

d)

Interpretation Introduction

Interpretation :

Number density of 22.4 L N₂ at STP must be found out.

Concept Introduction :

Number density of a gas sample is the number of gas molecules present in certain volume of gas sample. It can be also expressed in mol/L.

Answer to Problem 9RE

Number density for 22.4 L N₂ at STP is 0.045 mol/L.

Explanation of Solution

At STP 22.4 L N₂ gas is equal to 1 mol. As the volume is 22.4 L. Thus number density (n/V) $=\frac{1}{22.4}$ mol/L $=0.045$ mol/L.