Name: Law of Multiple Proportions
Uploaded: 2019-07-19
Duration: 6 min 43 s
Description: The Law of multiple proportions is applicable only when two elements combine to form two or more compounds. Watch this video to know how this law is applicable.

Question

2.50 g

sample of sodium bicarbonate when strongly heated gave

300 {cm}^{3}

of

{CO}_{2}

measured at

27 ° C

and

760 mm

pressure. Calculate the percentage purity of the sample.

Accepted Answer

The following reaction occurs when sodium bicarbonate strongly heated ;

$\underset{2 \times 84 g}{2 {NaHCO}_{3}} \to {Na}_{2} {CO}_{3} + H_{2} O + \underset{22400 {cm}^{3}}{{CO}_{2}}$

Given,

$P_{1} = 760 mm V_{1} = 300 {cm}^{3} T_{1} = 27 + 273 = 300 K$ and $P_{2} = 760 mm V_{2} = ? (Volume of {CO}_{2} gas at STP) T_{2} = 273 K$

Applying the gas equation,

$\frac{P_{1} V_{1}}{T_{1}} = \frac{P_{2} V_{2}}{T_{2}}$

$\frac{760 \times 300}{300} = \frac{760 \times V_{2}}{273} V_{2} = \frac{760 \times 300 \times 273}{300 \times 760} V_{2} = 273 {cm}^{3}$

The volume of ${CO}_{2}$ produced at STP = $273 {cm}^{3}$

$∵ 22400 {cm}^{3}$ of ${CO}_{2}$ gas is produced from $= (2 \times 84) g$ of the pure ${NaHCO}_{3}$ at STP

$∴ 273 {cm}^{3}$ of ${CO}_{2}$ gas will be produced from $= \frac{2 \times 84 \times 273}{22400} g$ of the pure ${NaHCO}_{3}$ at STP

$= 2.047 g$ of the pure ${NaHCO}_{3}$ at STP

Hence $2.047 g$ of the pure ${NaHCO}_{3}$ present in $2.50 g$ of an impure sample of ${NaHCO}_{3}$ .

$% purity = \frac{pure sample}{impure sample} \times 100 = \frac{2.047 \times 100}{2.50} = 81.9 %$

$2.50 g$ sample of sodium bicarbonate when strongly heated gave $300 {cm}^{3}$ of ${CO}_{2}$ measured at $27 ° C$ and $760 mm$ pressure. Calculate the percentage purity of the sample.

Important Questions on Some Basic Concepts of Chemistry

Learn and Prepare for any exam you want !

2.50 g sample of sodium bicarbonate when strongly heated gave 300 cm3 of CO2 measured at 27°C and 760 mm pressure. Calculate the percentage purity of the sample.

Important Questions on Some Basic Concepts of Chemistry

Learn and Prepare for any exam you want !

$2.50 g$ sample of sodium bicarbonate when strongly heated gave $300 {cm}^{3}$ of ${CO}_{2}$ measured at $27 ° C$ and $760 mm$ pressure. Calculate the percentage purity of the sample.