Question

A 1.1000 gram carbonate sample chosen from Li2CO3, K2CO3, Na2CO3 and CaCO3 was reacted with H2SO4 and was found to lose 0.3497 gram of CO2. (1) Show the calculation of the % CO2 in the unknown carbonate sample. (2) Show the calculation of the % CO2 in each of the carbonate compounds and identify the unknown carbonate from the list. Atomic weights: C = 12.01, O = 16.00. MWs: Li2CO3 = 73.892, K2CO3 = 138.21, Na2CO3 = 105.99 and CaCO3 = 100.09

Answer 1

Answer:

For 1: The percentage composition of $CO_2$ in unknown carbonate sample is 31.79 %

For 2: The unknown carbonate sample is potassium carbonate.

Explanation:

To calculate the percentage composition of carbon dioxide in sample, we use the equation:

$\%\text{ composition of }CO_2=\frac{\text{Mass of }CO_2}{\text{Mass of sample}}\times 100$     .....(1)

• For 1:

Mass of sample = 1.1000 g

Mass of carbon dioxide = 0.3497 g

Putting values in equation 1, we get:

$\%\text{ composition of }CO_2=\frac{0.3497g}{1.1000g}\times 100=31.79\%$

Hence, the percentage composition of $CO_2$ in unknown carbonate sample is 31.79 %

• For 2:

We are given:

Mass of carbon dioxide = $[1\times 12.01)+(2\times 16.00)]=44.01g$

• For lithium carbonate:

Mass of lithium carbonate= 73.892 g

Mass of carbon dioxide = 44.01 g

Putting values in equation 1, we get:

$\%\text{ composition of }CO_2=\frac{44.01g}{73.892g}\times 100=59.55\%$

The percent composition of carbon dioxide in lithium carbonate is 59.55 %

• For potassium carbonate:

Mass of potassium carbonate= 138.21 g

Mass of carbon dioxide = 44.01 g

Putting values in equation 1, we get:

$\%\text{ composition of }CO_2=\frac{44.01g}{138.21g}\times 100=31.84\%$

The percent composition of carbon dioxide in potassium carbonate is 31.84 %

• For sodium carbonate:

Mass of sodium carbonate= 105.99 g

Mass of carbon dioxide = 44.01 g

Putting values in equation 1, we get:

$\%\text{ composition of }CO_2=\frac{44.01g}{105.99g}\times 100=41.52\%$

The percent composition of carbon dioxide in sodium carbonate is 41.52 %

• For calcium carbonate:

Mass of calcium carbonate = 100.09 g

Mass of carbon dioxide = 44.01 g

Putting values in equation 1, we get:

$\%\text{ composition of }CO_2=\frac{44.01g}{100.09g}\times 100=43.97\%$

The percent composition of carbon dioxide in calcium carbonate is 43.97 %

As, the percent composition of carbon dioxide in the unknown sample matches the percent composition of carbon dioxide in potassium carbonate.

Hence, the unknown carbonate sample is potassium carbonate.