Question

Определите массовую долю кислорода в следующих веществах: NaOH, CuO, H3PO4, Ca(OH)2, Al2O3

Answer 1

NaOH 40 г/моль
CuO 80 г/моль
Н3РО4 98 г/моль

Answer 2

Determining the Mass Fraction of Oxygen in Substances

To determine the mass fraction of oxygen in the given substances, we can use their chemical formulas to calculate the molar mass and then find the mass fraction of oxygen in each substance.

1. Sodium Hydroxide (NaOH): - The molar mass of NaOH is 22.99 g/mol for Na, 15.999 g/mol for O, and 1.00794 g/mol for H. - The mass fraction of oxygen in NaOH can be calculated using the formula: \[ \text{Mass fraction of oxygen} = \frac{\text{Molar mass of oxygen}}{\text{Molar mass of NaOH}} \] - Calculating the mass fraction of oxygen in NaOH: \[ \frac{15.999 \, \text{g/mol}}{22.99 \, \text{g/mol} + 15.999 \, \text{g/mol} + 1.00794 \, \text{g/mol}} \approx 0.399 \] - The mass fraction of oxygen in NaOH is approximately 39.9%. [[8 #]]

2. Copper(II) Oxide (CuO): - The molar mass of CuO is 63.546 g/mol for Cu and 15.999 g/mol for O. - The mass fraction of oxygen in CuO can be calculated using the formula mentioned earlier. - Calculating the mass fraction of oxygen in CuO: \[ \frac{15.999 \, \text{g/mol}}{63.546 \, \text{g/mol} + 15.999 \, \text{g/mol}} \approx 0.201 \] - The mass fraction of oxygen in CuO is approximately 20.1%. [[4 #]]

3. Phosphoric Acid (H3PO4): - The molar mass of H3PO4 is 1.00794 g/mol for H, 15.999 g/mol for O, and 30.973761 g/mol for P. - The mass fraction of oxygen in H3PO4 can be calculated using the formula mentioned earlier. - Calculating the mass fraction of oxygen in H3PO4: \[ \frac{3 \times 15.999 \, \text{g/mol}}{3 \times 1.00794 \, \text{g/mol} + 3 \times 15.999 \, \text{g/mol} + 30.973761 \, \text{g/mol}} \approx 0.530 \] - The mass fraction of oxygen in H3PO4 is approximately 53.0%. [[8 #]]

4. Calcium Hydroxide (Ca(OH)2): - The molar mass of Ca(OH)2 is 40.078 g/mol for Ca, 15.999 g/mol for O, and 1.00794 g/mol for H. - The mass fraction of oxygen in Ca(OH)2 can be calculated using the formula mentioned earlier. - Calculating the mass fraction of oxygen in Ca(OH)2: \[ \frac{2 \times 15.999 \, \text{g/mol}}{40.078 \, \text{g/mol} + 2 \times 15.999 \, \text{g/mol} + 2 \times 1.00794 \, \text{g/mol}} \approx 0.474 \] - The mass fraction of oxygen in Ca(OH)2 is approximately 47.4%. [[8 #]]

5. Aluminum Oxide (Al2O3): - The molar mass of Al2O3 is 26.9815385 g/mol for Al and 15.999 g/mol for O. - The mass fraction of oxygen in Al2O3 can be calculated using the formula mentioned earlier. - Calculating the mass fraction of oxygen in Al2O3: \[ \frac{3 \times 15.999 \, \text{g/mol}}{2 \times 26.9815385 \, \text{g/mol} + 3 \times 15.999 \, \text{g/mol}} \approx 0.470 \] - The mass fraction of oxygen in Al2O3 is approximately 47.0%. [[5 #]]

In summary: - NaOH: Approximately 39.9% oxygen - CuO: Approximately 20.1% oxygen - H3PO4: Approximately 53