212k views
1 vote
SHOW YOUR WORK

1. A sample of Copper(II) sulfate hydrate has a mass of 3.97g. After heating, the CuSO4 that remains has a mass of 2.54g. Determine the correct formula and name of the hydrate.
2. A sample of the hydrate of sodium carbonate has a mass of 8.85g. It loses 1.28g when heated. Find the formula and the name of the hydrate.

User Nolik
by
8.0k points

1 Answer

6 votes

Answer:

carbonate has a mass of 4.56g. After heating, the anhydrous salt that remains has a mass of 3.12g. Determine the correct formula and name of the hydrate.

1. To determine the formula and name of the hydrate, we need to find the mass of water that was originally present in the sample.

Mass of CuSO4 before heating = 3.97g

Mass of CuSO4 after heating = 2.54g

Mass of water lost = 3.97g - 2.54g = 1.43g

To find the number of moles of CuSO4 and water, we use their respective molar masses:

Molar mass of CuSO4 = 63.55g/mol

Molar mass of H2O = 18.015g/mol

Moles of CuSO4 = 2.54g / 63.55g/mol = 0.04 mol

Moles of H2O = 1.43g / 18.015g/mol = 0.079 mol

Next, we divide the moles of CuSO4 and H2O by the smallest number of moles to obtain the simplest, whole-number ratio of the two:

CuSO4 : H2O = 0.04/0.04 : 0.079/0.04 = 1 : 1.98 (rounded to 2)

Therefore, the formula of the hydrate is CuSO4 · 2H2O, and the name is copper(II) sulfate dihydrate.

To find the formula of the hydrate, we need to determine the mass of the anhydrous salt (without water).

Mass of hydrate = 8.85g

Mass of anhydrous salt = 8.85g - 1.28g = 7.57g

The formula of the hydrate can be determined by calculating the ratio of moles of anhydrous salt to moles of water.

Moles of anhydrous salt = 7.57g / 106g/mol = 0.0713 mol

Moles of water lost = 1.28g / 18g/mol = 0.0711 mol

The ratio of moles is approximately 1:1, suggesting that the formula of the hydrate is Na2CO3·H2O.

The name of the hydrate is sodium carbonate monohydrate.

User Kintela
by
8.1k points