Question

Гидроксид бария массой 8,55 г растворили в соляной кислоте. Из этого раствора был получен кристаллогидрат массой 12,2 г. Определите формулу кристаллогидрата

Answer 1

  8,55г           --------        12,2 г
                               ------------------
Ba(OH)2 + 2HCı = BaCl2 +2H2O
                               ------------------
171г            ---------         х г           х=244г
значть формула кристалгидрата : BaCl2*2H2O
 

Answer 2

Problem Analysis

We are given that 8.55 g of barium hydroxide (Ba(OH)2) was dissolved in hydrochloric acid (HCl), and from this solution, a crystal hydrate with a mass of 12.2 g was obtained. We need to determine the formula of the crystal hydrate.

Solution

To find the formula of the crystal hydrate, we need to calculate the molar mass of the anhydrous compound (Ba(OH)2) and the molar mass of the water molecule (H2O). Then we can calculate the ratio of the two components in the crystal hydrate.

1. Calculate the molar mass of Ba(OH)2: - The molar mass of Ba is 137.33 g/mol. - The molar mass of O is 16.00 g/mol. - The molar mass of H is 1.01 g/mol. - Ba(OH)2 has one barium atom, two hydroxide ions, and two hydrogen atoms. - The molar mass of Ba(OH)2 is calculated as follows: ``` Molar mass of Ba(OH)2 = (1 * molar mass of Ba) + (2 * molar mass of O) + (2 * molar mass of H) = (1 * 137.33) + (2 * 16.00) + (2 * 1.01) = 137.33 + 32.00 + 2.02 = 171.35 g/mol ```

2. Calculate the molar mass of H2O: - The molar mass of H2O is calculated as follows: ``` Molar mass of H2O = (2 * molar mass of H) + (1 * molar mass of O) = (2 * 1.01) + 16.00 = 2.02 + 16.00 = 18.02 g/mol ```

3. Calculate the ratio of Ba(OH)2 to H2O in the crystal hydrate: - The mass of Ba(OH)2 in the crystal hydrate can be calculated using the mass of the anhydrous compound and the mass of the water: ``` Mass of Ba(OH)2 = Mass of crystal hydrate - Mass of H2O = 12.2 g - 8.55 g = 3.65 g ``` - The number of moles of Ba(OH)2 can be calculated using the molar mass of Ba(OH)2: ``` Moles of Ba(OH)2 = Mass of Ba(OH)2 / Molar mass of Ba(OH)2 = 3.65 g / 171.35 g/mol = 0.0213 mol ``` - The number of moles of H2O can be calculated using the molar mass of H2O: ``` Moles of H2O = Mass of H2O / Molar mass of H2O = 8.55 g / 18.02 g/mol = 0.474 mol ``` - The ratio of Ba(OH)2 to H2O in the crystal hydrate is approximately 0.0213 mol : 0.474 mol, which simplifies to 1 : 22.3.

4. Determine the formula of the crystal hydrate: - The formula of the crystal hydrate is Ba(OH)2 · 22.3H2O.

Answer

The formula of the crystal hydrate is Ba(OH)2 · 22.3H2O.