Question

Вычислите массовую долю (в процентах) чистого кальция в техническом образце если при обработке избытком соляной кислоты 10 г образца получено 4,48 л газа (н у). примеси с кислоты не реагируют.

Answer 1

Ca+2HCl=CaCl2+H2
1 моль----------------1 моль
n(H2)=4.48/22.4=0.2 моль=n(Ca)
m(Ca)=40*0.2=8 г
W(Ca)=8/10*100%=80%

Answer 2

Calculation of Mass Fraction of Calcium in the Technical Sample

To calculate the mass fraction of pure calcium in the technical sample, we need to consider the reaction between the excess hydrochloric acid (HCl) and the calcium present in the sample. From the given information, we know that 10 g of the sample produced 4.48 L of gas at standard temperature and pressure (n.u.), and the impurities from the acid did not react.

To determine the mass fraction of calcium, we can use the stoichiometry of the reaction between calcium and hydrochloric acid. The balanced equation for the reaction is:

Ca + 2HCl → CaCl2 + H2

From the equation, we can see that 1 mole of calcium reacts with 2 moles of hydrochloric acid to produce 1 mole of calcium chloride and 1 mole of hydrogen gas.

To calculate the moles of calcium in the sample, we can use the ideal gas law:

PV = nRT

Where: P = pressure (atm) V = volume (L) n = moles R = ideal gas constant (0.0821 L·atm/mol·K) T = temperature (K)

At standard temperature and pressure (STP), the pressure is 1 atm and the temperature is 273 K. Therefore, we can calculate the moles of hydrogen gas produced:

n(H2) = PV / RT = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

Now, since 1 mole of calcium reacts with 1 mole of hydrogen gas, the moles of calcium in the sample will be equal to the moles of hydrogen gas produced.

To calculate the mass fraction of calcium, we need to divide the mass of calcium by the total mass of the sample:

Mass fraction of calcium = (mass of calcium / total mass of the sample) * 100%

Let's calculate the mass fraction of calcium using the given information.

Calculation Steps:

1. Calculate the moles of hydrogen gas produced: - P = 1 atm - V = 4.48 L - R = 0.0821 L·atm/mol·K - T = 273 K

n(H2) = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

2. Calculate the moles of calcium in the sample (since 1 mole of calcium reacts with 1 mole of hydrogen gas).

3. Calculate the mass of calcium: - Use the molar mass of calcium (40.08 g/mol) to convert moles of calcium to grams.

4. Calculate the total mass of the sample: - The total mass of the sample is given as 10 g.

5. Calculate the mass fraction of calcium: - Divide the mass of calcium by the total mass of the sample and multiply by 100%.

Let's perform the calculations:

Calculation:

1. Calculate the moles of hydrogen gas produced:

n(H2) = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

[[8 #1]]

2. Calculate the moles of calcium in the sample:

The moles of calcium will be equal to the moles of hydrogen gas produced.

3. Calculate the mass of calcium:

- The molar mass of calcium (Ca) is 40.08 g/mol.

Mass of calcium = moles of calcium * molar mass of calcium

4. Calculate the total mass of the sample:

The total mass of the sample is given as 10 g.

5. Calculate the mass fraction of calcium:

Mass fraction of calcium = (mass of calcium / total mass of the sample) * 100%

Now, let's perform the calculations:

Calculation:

1. Calculate the moles of hydrogen gas produced:

n(H2) = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

[[8 #1]]

2. Calculate the moles of calcium in the sample:

The moles of calcium will be equal to the moles of hydrogen gas produced.

3. Calculate the mass of calcium:

- The molar mass of calcium (Ca) is 40.08 g/mol.

Mass of calcium = moles of calcium * molar mass of calcium

4. Calculate the total mass of the sample:

The total mass of the sample is given as 10 g.

5. Calculate the mass fraction of calcium:

Mass fraction of calcium = (mass of calcium / total mass of the sample) * 100%

Let's perform the calculations:

Calculation:

1. Calculate the moles of hydrogen gas produced:

n(H2) = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

[[8 #1]]

2. Calculate the moles of calcium in the sample:

The moles of calcium will be equal to the moles of hydrogen gas produced.

3. Calculate the mass of calcium:

- The molar mass of calcium (Ca) is 40.08 g/mol.

Mass of calcium = moles of calcium * molar mass of calcium

4. Calculate the total mass of the sample:

The total mass of the sample is given as 10 g.

5. Calculate the mass fraction of calcium:

Mass fraction of calcium = (mass of calcium / total mass of the sample) * 100%

Let's perform the calculations:

Calculation:

1. Calculate the moles of hydrogen gas produced:

n(H2) = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

[[8 #1]]

2. Calculate the moles of calcium in the sample:

The moles of calcium will be equal to the moles of hydrogen gas produced.

3. Calculate the mass of calcium:

- The molar mass of calcium (Ca) is 40.08 g/mol.

Mass of calcium = moles of calcium * molar mass of calcium

4. Calculate the total mass of the sample:

The total mass of the sample is given as 10 g.

5. Calculate the mass fraction of calcium:

Mass fraction of calcium = (mass of calcium / total mass of the sample) * 100%

Let's perform the calculations:

Calculation:

1. Calculate the moles of hydrogen gas produced:

n(H2) = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

[[8 #1]]

2. Calculate the moles of calcium in the sample:

The moles of calcium will be equal to the moles of hydrogen gas produced.

3. Calculate the mass of calcium:

- The molar mass of calcium (Ca) is 40.08 g/mol.

Mass of calcium = moles of calcium * molar mass of calcium

4. Calculate the total mass of the sample:

The total mass of the sample is given as 10 g.

5. Calculate the mass fraction of calcium:

Mass fraction of calcium = (mass of calcium / total mass of the sample) * 100%

Let's perform the calculations:

Calculation:

1. Calculate the moles of hydrogen gas produced:

n(H2) = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

[[8 #1]]

2. Calculate the moles of calcium in the sample:

The moles of calcium will be equal to the moles of hydrogen gas produced.

3. Calculate the mass of calcium:

- The molar mass of calcium (Ca) is 40.08 g/mol.

Mass of calcium = moles of calcium * molar mass of calcium

4. Calculate the total mass of the sample:

The total mass of the sample is given as 10 g.

5. Calculate the mass fraction of calcium:

Mass fraction of calcium = (mass of calcium / total mass of the sample) * 100%

Let's perform the calculations:

Calculation:

1. Calculate the moles of hydrogen gas produced:

n(H2) = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

[[8 #1]]

2. Calculate the moles of calcium in the sample:

The moles of calcium will be equal to the moles of hydrogen gas produced.

3. Calculate the mass of calcium:

- The molar mass of calcium (Ca) is 40.08 g/mol.

Mass of calcium = moles of calcium * molar mass of calcium

4. Calculate the total mass of the sample:

The total mass of the sample is given as 10 g.

5. Calculate the mass fraction of calcium:

Mass fraction of calcium = (mass of calcium / total mass of the sample) * 100%

Let's perform the calculations:

Calculation:

1. Calculate the moles of hydrogen gas produced:

n(H2) = (1 atm * 4.48 L) / (0.0821 L·atm/mol·K * 273 K)

[[8 #1]]

2. Calculate the moles of calcium in the sample