Question

1) После обработки 23,7 г смеси аллюминия и его оксида избытком концентрированного раствора гидроксида натрия собрали 16,8 л газа (н.у.) Определите массовую долю (%) оксида аллюминия в исходной смеси.

Answer 1

Ответ: 43%

Объяснение:

Answer 2

Calculation of Mass Fraction of Aluminum Oxide

To determine the mass fraction of aluminum oxide in the initial mixture, we need to use the given information about the volume of gas collected and the balanced chemical equation for the reaction.

The balanced chemical equation for the reaction is as follows:

2Al + 3NaOH + 3H2O -> 3NaAlO2 + 3H2

From the equation, we can see that 2 moles of aluminum react with 3 moles of sodium hydroxide to produce 3 moles of sodium aluminate and 3 moles of hydrogen gas.

Given that 16.8 liters of gas (at standard temperature and pressure) were collected, we can convert this volume to moles of hydrogen gas using the ideal gas law. Since the molar ratio between hydrogen gas and aluminum oxide is 3:3, we can determine the moles of aluminum oxide produced.

Next, we need to determine the moles of aluminum in the initial mixture. Since the molar ratio between aluminum and aluminum oxide is 2:3, we can calculate the moles of aluminum.

Finally, we can calculate the mass fraction of aluminum oxide by dividing the moles of aluminum oxide by the total moles of the mixture (aluminum + aluminum oxide).

Let's perform the calculations:

1. Convert the volume of gas collected to moles of hydrogen gas: - Using the ideal gas law, we can convert the volume of gas to moles: - PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature. - At standard temperature and pressure (STP), the pressure is 1 atm and the temperature is 273.15 K. - Assuming the gas collected is hydrogen gas, the molar volume at STP is 22.4 liters/mol. - Therefore, the number of moles of hydrogen gas can be calculated as follows: - n = (V * P) / (R * T) = (16.8 * 1) / (0.0821 * 273.15) mol

2. Calculate the moles of aluminum oxide: - Since the molar ratio between hydrogen gas and aluminum oxide is 3:3, the moles of aluminum oxide produced is equal to the moles of hydrogen gas collected.

3. Calculate the moles of aluminum: - Since the molar ratio between aluminum and aluminum oxide is 2:3, the moles of aluminum is calculated as follows: - Moles of aluminum = (2/3) * Moles of aluminum oxide

4. Calculate the total moles of the mixture: - Total moles of the mixture = Moles of aluminum + Moles of aluminum oxide

5. Calculate the mass fraction of aluminum oxide: - Mass fraction of aluminum oxide = (Moles of aluminum oxide / Total moles of the mixture) * 100

Let's perform the calculations using the given data:

1. Convert the volume of gas collected to moles of hydrogen gas: - n = (16.8 * 1) / (0.0821 * 273.15) mol = 0.757 mol

2. Calculate the moles of aluminum oxide: - Moles of aluminum oxide = 0.757 mol

3. Calculate the moles of aluminum: - Moles of aluminum = (2/3) * 0.757 mol = 0.505 mol

4. Calculate the total moles of the mixture: - Total moles of the mixture = 0.757 mol + 0.505 mol = 1.262 mol

5. Calculate the mass fraction of aluminum oxide: - Mass fraction of aluminum oxide = (0.757 mol / 1.262 mol) * 100 = 59.97%

Therefore, the mass fraction of aluminum oxide in the initial mixture is approximately 59.97%.