Question

A common issue in organic chemistry processes is trace contamination. Organic solvents can become contaminated with water. One method of removing the water contamination is to freeze dry the solvent. Unfortunately, not all solvents, like acetonitrile, are compatible with this method. Another method is to add a chemical to react with the water. One such chemical is calcium hydride, which will react to form calcium hydroxide and hydrogen gas. When you checked the chemical inventory, you realized you only had 24.6g of calcium hydride on hand. If you had a 1.5L container of organic solvent that contained 14.0g of water, what will be the outcome of your attempt to dewater the solvent?

Answer 1

Complete Question

A common issue in organic chemistry processes is trace contamination. Organic solvents can become contaminated with water. One method of removing the water contamination is to freeze dry the solvent. Unfortunately, not all solvents, like acetonitrile, are compatible with this method. Another method is to add a chemical to react with the water. One such chemical is calcium hydride, which will react to form calcium hydroxide and hydrogen gas. When you checked the chemical inventory, you realized you only had 24.6g of calcium hydride on hand. If you had a 1.5L container of organic solvent that contained 14.0g of water, what will be the outcome of your attempt to dewater the solvent?

A ) There is no way to tell

B) CaH2 will be left over

C water will be left over

D Both will be left over

Answer:

The correct option is B

Explanation:

From the question we are told that

The mass of calcium hydride present is $m_h = 24.6 \ g$

The mass of water is $m_w = 14.0 \ g$

Generally the molar mass of calcium hydride is $Z_h = 42 \ g/mol$

The molar mass of water is $Z_w = 18 \ g / mol$

The reaction between water and calcium hydride can be represented as a balanced chemical equation as follows

$CaH_2 + 2 H_2O \to Ca(OH)_2 + 2H_2$

From this equation we see that

1 mole(42 g) of calcium hydride dries 2(2 * 18 g) moles of water

Then we can say that

if 42 grams of calcium hydride dries (2 * 18 )g of water

24.6 grams will dry z grams of water

=> $z = \frac{24.6 * 2 *18}{42}$

=>     $z = 21.1 \ g$ of  water

Given that the amount of water the 24.6g of  calcium hydride is capable  of drying is greater than the amount of  water present then the it means that after drying the water available that the calcium hydride will remain