Question

Water is evaporated from a sample calcium chloride hydrate. The sample is found to contain

1.110 grams CaCl2 and 1.081 grams of water. What is the formula of the hydrate?

Answer 1

Step-by-step explanation:

To determine the formula of a hydrate, we need to calculate the number of moles of calcium chloride and water in the sample, and then use the mole ratios to determine the empirical formula of the hydrate.

First, we'll calculate the number of moles of calcium chloride:

1.110 g CaCl2 / (110.98 g/mol) = 0.01 moles CaCl2

Next, we'll calculate the number of moles of water:

1.081 g H2O / (18.015 g/mol) = 0.06 moles H2O

Now that we have the number of moles of each component, we can determine the mole ratio of calcium chloride to water:

0.01 moles CaCl2 / 0.06 moles H2O = 1/6

This means that for every 6 moles of water, there is 1 mole of calcium chloride. Based on this information, the empirical formula of the hydrate can be written as CaCl2 · 6H2O.

Note that the empirical formula represents the simplest whole-number ratio of atoms in a compound and does not necessarily represent the true molecular formula, which may be a multiple of the empirical formula. To determine the true molecular formula, we would need additional information, such as the molecular weight of the compound.

Answer 2

To determine the formula of the hydrate, you need to calculate the ratio of water to the salt (CaCl2) in the hydrate. You can do this by dividing the mass of water by the mass of the salt and then determining the simplest whole number ratio that represents this value.

1.081 g H2O / 1.110 g CaCl2 = 0.970

Since the ratio is close to 1:1, we can assume that the formula of the hydrate is CaCl2 * H2O, with one mole of water for every mole of CaCl2. So the formula of the hydrate would be CaCl2.H2O.