Gravimetric analysis does not always involve a precipitate. Consider the following problem. A mixture of calcium carbonate and calium oxide has a mass of 8.35 grams. When heated strongly, the CaCO3 in the sample decomposes into solid CaO and carbon dioxide gas. The calcium oxide in the original sample is not altered by heating. After heating, the mass of the sample is 6.37 grams. Using the information given, calculate the % by mass of calcium oxide in the original sample.

To calculate the percentage by mass of calcium oxide in the original sample, we need to determine the mass of CaO formed during the decomposition of CaCO3 and then use that information to calculate the percentage.

Step 1: Calculate the mass of CaO formed.
Given that the original sample had a mass of 8.35 grams and after heating, the mass became 6.37 grams, we can calculate the mass of CaO formed.
Mass of CaO formed = Mass of original sample - Mass after heating
= 8.35 g - 6.37 g
= 1.98 g

Step 2: Calculate the percentage by mass of CaO in the original sample.
Percentage by mass of CaO = (Mass of CaO formed / Mass of original sample) * 100%
= (1.98 g / 8.35 g) * 100%
≈ 23.7%

Therefore, the % by mass of calcium oxide (CaO) in the original sample is approximately 23.7%.

To calculate the percent by mass of calcium oxide in the original sample, we need to determine the amount of calcium oxide and the total mass of the original sample.

Here's how you can approach this problem:

1. Determine the mass of calcium oxide in the sample after heating.
- Subtract the mass of the sample after heating (6.37 grams) from the mass of the initial sample (8.35 grams).
- The difference will give you the mass of calcium oxide: 8.35 g - 6.37 g = 1.98 grams.

2. Determine the total mass of the original sample.
- The total mass of the original sample is given as 8.35 grams.

3. Calculate the percent by mass of calcium oxide.
- Divide the mass of calcium oxide (1.98 grams) by the total mass of the original sample (8.35 grams).
- Multiply the result by 100 to bring the answer into percentage form.
- (1.98 g / 8.35 g) * 100 = 23.69230769... ≈ 23.7%

Therefore, the percent by mass of calcium oxide in the original sample is approximately 23.7%.