A sample of mix. Of cacl2 and nacl weighing 5.55 gm was treated to precipitate all the ca as caco3 which was then heated and quantitively conv. To 1.68gm of cao . Calculate the mass percentage of cacl2in mix.

To determine the mass percentage of calcium chloride (CaCl2) in the mixture, we need to follow a series of logical steps based on the information provided. The process involves understanding the chemical reactions and performing some calculations. Let’s break it down step by step.

Step 1: Understanding the Chemical Reactions

When the mixture of CaCl2 and NaCl is treated to precipitate calcium as calcium carbonate (CaCO3), the reaction can be represented as follows:

• CaCl2 + Na2CO3 → CaCO3 (s) + 2 NaCl

After precipitating, the CaCO3 is heated to convert it into calcium oxide (CaO) through the following reaction:

• CaCO3 (s) → CaO (s) + CO2 (g)

Step 2: Relating Mass of CaO to Mass of CaCl2

From the problem, we know that the final mass of CaO obtained is 1.68 g. To find out how much CaCl2 was in the original mixture, we need to relate the mass of CaO back to the mass of CaCl2. The molar masses are essential here:

• Molar mass of CaO = 40.08 (Ca) + 16.00 (O) = 56.08 g/mol
• Molar mass of CaCO3 = 40.08 (Ca) + 12.01 (C) + 16.00 (O) × 3 = 100.09 g/mol
• Molar mass of CaCl2 = 40.08 (Ca) + 35.45 (Cl) × 2 = 110.98 g/mol

Step 3: Calculating Moles of CaO

Next, we calculate the number of moles of CaO produced:

Number of moles of CaO = mass / molar mass = 1.68 g / 56.08 g/mol ≈ 0.0299 mol

Step 4: Finding Moles of CaCO3 and CaCl2

Since one mole of CaCO3 produces one mole of CaO, the moles of CaCO3 formed are also 0.0299 mol. Now, using the stoichiometry of the reaction, we can find the moles of CaCl2:

From the reaction, 1 mole of CaCl2 produces 1 mole of CaCO3. Therefore, moles of CaCl2 = moles of CaCO3 = 0.0299 mol.

Step 5: Calculating Mass of CaCl2

Now, we can find the mass of CaCl2 in the mixture:

Mass of CaCl2 = moles × molar mass = 0.0299 mol × 110.98 g/mol ≈ 3.32 g

Step 6: Determining Mass Percentage of CaCl2

Finally, to find the mass percentage of CaCl2 in the original mixture, we use the formula:

Mass percentage of CaCl2 = (mass of CaCl2 / total mass of mixture) × 100

Substituting the values:

Mass percentage of CaCl2 = (3.32 g / 5.55 g) × 100 ≈ 59.84%

Final Result

Thus, the mass percentage of calcium chloride (CaCl2) in the mixture is approximately 59.84%.