10 gram of caco3 (s) and na2co3(s) when heated strongly left a residue which is weighing 6.7 gram .the mass percent of caco3 in the mixture

To determine the mass percent of calcium carbonate (CaCO3) in the mixture of CaCO3 and sodium carbonate (Na2CO3) after heating, we need to analyze the chemical reactions that occur during the heating process. When heated, both compounds decompose, but they do so in different ways. Let's break this down step by step.

Understanding the Reactions

When heated, calcium carbonate decomposes into calcium oxide (CaO) and carbon dioxide (CO2) according to the following reaction:

• CaCO3 (s) → CaO (s) + CO2 (g)

Sodium carbonate, on the other hand, does not decompose upon heating but remains as Na2CO3. Therefore, the residue after heating will consist of the calcium oxide formed from CaCO3 and the unchanged sodium carbonate.

Setting Up the Problem

Let’s denote the mass of CaCO3 in the mixture as x grams. Consequently, the mass of Na2CO3 would be (10 - x) grams, since the total mass of the mixture is 10 grams.

Calculating the Mass of the Residue

After heating, the mass of the residue consists of the calcium oxide produced from the decomposition of CaCO3 and the sodium carbonate that remains unchanged. The molar masses of the compounds are as follows:

• CaCO3: 100.09 g/mol
• CaO: 56.08 g/mol
• Na2CO3: 105.99 g/mol

From the reaction, we know that 1 mole of CaCO3 produces 1 mole of CaO. Therefore, the mass of CaO produced from x grams of CaCO3 can be calculated using the ratio of their molar masses:

Mass of CaO = (x grams of CaCO3) × (56.08 g/mol CaO / 100.09 g/mol CaCO3)

Now, the mass of Na2CO3 remains unchanged, which is (10 - x) grams. Thus, the total mass of the residue after heating can be expressed as:

Residue mass = Mass of CaO + Mass of Na2CO3

Substituting the values, we have:

6.7 g = (x × 56.08 / 100.09) + (10 - x)

Solving the Equation

Now, let's solve for x:

6.7 = (x × 56.08 / 100.09) + 10 - x

Rearranging gives:

x × 56.08 / 100.09 + x = 10 - 6.7

x × (56.08 / 100.09 + 1) = 3.3

x × (0.5608 + 1) = 3.3

x × 1.5608 = 3.3

x = 3.3 / 1.5608 ≈ 2.11 grams

Finding the Mass Percent of CaCO3

Now that we have the mass of CaCO3, we can find the mass percent of CaCO3 in the original mixture:

Mass percent of CaCO3 = (mass of CaCO3 / total mass of mixture) × 100

Mass percent of CaCO3 = (2.11 g / 10 g) × 100 ≈ 21.1%

Final Thoughts

Thus, the mass percent of calcium carbonate in the original mixture is approximately 21.1%. This calculation illustrates how chemical reactions and stoichiometry can be applied to determine the composition of mixtures after thermal processes. If you have any further questions or need clarification on any steps, feel free to ask!