In an experiment a 40,88g sample of inc reacted with hydrochloric acid; ZN+2HCL-ZnCl2+H2

Question

It was found that 68g of ZnCL2 formed

a) Calculate the number of moles of ZnCl2 that formed.
b) Calculate the percentage of purity of the sample.
c) Calculate the concentration of the HCL if 0,2 dm cube HCL has reacted with the Zn.

Answer 1

To calculate the number of moles of ZnCl2 that formed, we need to use its molar mass.

a) The molar mass of ZnCl2 is 136.29 g/mol.
Number of moles of ZnCl2 = mass of ZnCl2 formed / molar mass of ZnCl2
= 68g / 136.29 g/mol
= 0.5 moles

b) To calculate the percentage of purity of the sample, we need to compare the number of moles of ZnCl2 formed with the theoretical maximum number of moles of ZnCl2 that could have formed.

The balanced chemical equation tells us that 1 mole of Zn reacts with 2 moles of HCl to form 1 mole of ZnCl2. So if 0.5 moles of ZnCl2 formed, it means that 0.5 moles of Zn reacted.

Number of moles of Zn in the sample = number of moles of ZnCl2 formed
= 0.5 moles

Percentage of purity = (number of moles of Zn / total number of moles in the sample) * 100

We need to find the total number of moles in the sample. The molar mass of Zn is 65.38 g/mol.

Mass of Zn in the sample = mass of the sample - mass of ZnCl2 formed
= 40.88g - 68g
= -27.12g

Since we cannot have a negative mass, it means that the sample was not pure. The negative mass indicates that there was an impurity present in the sample. Therefore, it is not possible to determine the percentage of purity of the sample in this case.

c) To calculate the concentration of HCl, we need to use the volume and moles of HCl used in the reaction. From the balanced chemical equation, we know that 1 mole of Zn reacts with 2 moles of HCl. Therefore, the number of moles of HCl used is double the number of moles of Zn.

Number of moles of HCl = 2 * number of moles of Zn
= 2 * 0.5 moles
= 1 mole

Concentration of HCl = number of moles / volume of HCl
= 1 mole / 0.2 dm^3
= 5 mol/dm^3