What is the mass percent of CaCO3 in a mixture after heating to produce CO2?

[sexpillus]

Homework Statement

mixture of CaCO3 and CaO m=0.656 g, heated to produce CO2. After heating, only CaO solid remains and it weighs 0.485 g.

Assuming all the CaCO3 decomposed to CaO and CO2, calculate the mass percent of CaCO3 in the original mixture.

Homework Equations

The Attempt at a Solution

I have no clue how to start this off. The answer is 59.3

 

[Borek]

Do it backward, For known amount of CO₂ produced, calculate mass of CaCO₃ decomposed. This is a simple stoichiometry - start with the balanced reaction equation.

 

[Blueshift5]

%.

To solve this problem, we can use the formula for mass percent:

Mass percent = (mass of component/total mass of mixture) x 100%

In this case, the component we are interested in is CaCO3, and the total mass of the mixture is 0.656 g. We know that after heating, only CaO remains, which has a mass of 0.485 g. Therefore, the mass of CaCO3 that decomposed to form CaO and CO2 is 0.656 g - 0.485 g = 0.171 g.

Using the formula, we can calculate the mass percent of CaCO3:

Mass percent of CaCO3 = (0.171 g / 0.656 g) x 100% = 26.1%

However, this is not the mass percent of CaCO3 in the original mixture, since some CaCO3 remained unreacted. To find the mass percent in the original mixture, we need to take into account the fact that CaCO3 accounts for only 26.1% of the total mass after heating. Therefore, we can set up the following equation:

0.261 x total mass = 0.656 g

Solving for the total mass, we get:

Total mass = 0.656 g / 0.261 = 2.51 g

Now, we can calculate the mass percent of CaCO3 in the original mixture using the formula:

Mass percent of CaCO3 = (mass of CaCO3 / total mass) x 100%

Plugging in the values, we get:

Mass percent of CaCO3 = (0.656 g / 2.51 g) x 100% = 59.3%

Therefore, the mass percent of CaCO3 in the original mixture is 59.3%. This is the percentage of the original mixture that was made up of CaCO3 before it decomposed to form CaO and CO2.