Question

Смесь железа и кремния массой 15 г обработали соляной кислотой, при этом выделилось 5,6 л газа(н.у). Определите массовую долю кремния в смеси.

Answer 1

Из смеси железа с кремнием с соляной кислотой реагирует только железо.

Fe+2HCl-->FeCl2+H2↑

Итак, выделившийся газ - водород, найдем его хим. кол-во:
n(H2)=V/Vm=5,6л/22,4л/моль=0,25 моль
Тогда n(Fe)=n(H2)=0,25 моль

Найдем массу железа:
m(Fe)=n*M=0,25моль*56г/моль=14 г
Тогда m(Si)=15г-14г=1 г

Найдем массовую долю кремния:
w(Si)=1г/15г=0,0667 (6,67%)

Answer 2

Calculation of the Silicon Mass Fraction in the Mixture

To determine the mass fraction of silicon in the mixture, we need to use the information provided. The mixture consists of iron and silicon with a total mass of 15 g. When the mixture is treated with hydrochloric acid, 5.6 L of gas is released at standard temperature and pressure (n.u).

To calculate the mass fraction of silicon, we need to find the mass of silicon in the mixture. We can use the ideal gas law to relate the volume of gas released to the number of moles of gas produced. From there, we can determine the number of moles of silicon and calculate its mass.

Let's proceed with the calculations step by step:

1. Convert the volume of gas released to the number of moles using the ideal gas law. The ideal gas law equation is given by:

PV = nRT

Where: - P is the pressure of the gas (at standard temperature and pressure, P = 1 atm) - V is the volume of the gas (5.6 L) - n is the number of moles of gas (to be determined) - R is the ideal gas constant (0.0821 L·atm/mol·K) - T is the temperature in Kelvin (standard temperature and pressure, T = 273.15 K)

Rearranging the equation to solve for n:

n = PV / RT

Substituting the values:

n = (1 atm) * (5.6 L) / (0.0821 L·atm/mol·K * 273.15 K)

Calculating n:

n ≈ 0.232 mol

2. Since the gas released is assumed to be hydrogen gas (H2) due to the reaction of hydrochloric acid with the mixture, the number of moles of silicon is equal to the number of moles of hydrogen gas produced.

Therefore, the number of moles of silicon is approximately 0.232 mol.

3. To calculate the mass of silicon, we need to know the molar mass of silicon (Si). The molar mass of silicon is approximately 28.09 g/mol.

Multiplying the number of moles of silicon by the molar mass of silicon:

Mass of silicon = 0.232 mol * 28.09 g/mol

Calculating the mass of silicon:

Mass of silicon ≈ 6.51 g

4. Finally, to determine the mass fraction of silicon in the mixture, we divide the mass of silicon by the total mass of the mixture and multiply by 100:

Mass fraction of silicon = (Mass of silicon / Total mass of mixture) * 100

Substituting the values:

Mass fraction of silicon = (6.51 g / 15 g) * 100

Calculating the mass fraction of silicon:

Mass fraction of silicon ≈ 43.4%

Therefore, the mass fraction of silicon in the mixture is approximately 43.4%.

Please note that the calculations provided are based on the assumption that the gas released is hydrogen gas (H2) due to the reaction with hydrochloric acid. If the gas released is different, the calculations may vary.