Chapter 5, Problem 81QAP

Interpretation Introduction

(a)

Interpretation:

A ‘before’ sketch showing a cylinder attached to a piston initially containing 10 molecules of He gas needs to be depicted. An ‘after’ sketch representing a decrease in temperature at constant pressure also needs to be depicted.

Concept introduction:

The ideal gas equation is a thermodynamic equation of state which relates the pressure (P), volume (V), number of moles (n) and temperature (T) of an ideal gas through the following expression:

$\text{PV = nRT -----(1)}$

Where R is the universal gas constant = 0.0821 L.atm/mol-K

When the temperature is decreased at constant pressure (and keeping the moles (n) constant) then volume will also decrease since ‘V’ is directly proportional to ‘T’.

It is mathematically represented as follows:

$\frac{V_1}{V_2}\text{= }\frac{T_1}{T_2}$

Interpretation Introduction

(b)

Interpretation:

A ‘before’ sketch showing a cylinder attached to a piston initially containing 10 molecules of He gas needs to be depicted. An ‘after’ sketch representing a decrease in pressure from 1000 mmHg to 500 mmHg at constant temperature also needs to be depicted.

Concept introduction:

When number of moles and temperature is constant and change in pressure takes place. The relation between pressure and volume is using ideal gas equation is as follows:

${\text{P}}_1{\text{V}}_1{\text{ =P}}_2{\text{V}}_2$

Here, P is pressure and V is volume.

Interpretation Introduction

(c)

Interpretation:

A ‘before’ sketch showing a cylinder attached to a piston initially containing 10 molecules of He gas needs to be depicted. An ‘after’ sketch representing an addition of 5 molecules of H₂ gas at constant temperature and pressure also needs to be depicted.

Concept introduction:

Noble gases do not react with the any gas added to the system. In such cases, the total number of moles of system become equal to the sum of number of moles of noble gas and the added gas.