In an experiment a 40,88g sample of inc reacted with hydrochloric acid; ZN+2HCL-ZnCl2+H2
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.
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
To answer these questions, we will follow these steps:
Step 1: Calculate the number of moles of ZnCl2 formed.
Step 2: Calculate the molar mass of ZnCl2.
Step 3: Use the molar mass of ZnCl2 to find the number of moles.
Step 4: Calculate the percentage of purity of the sample.
Step 5: Calculate the concentration of HCl using stoichiometry.
Let's start with step 1:
Step 1: Calculate the number of moles of ZnCl2 that formed.
Given: Mass of ZnCl2 = 68 g.
We will use the formula:
moles = mass / molar mass
The molar mass of ZnCl2 can be calculated as:
Molar mass of ZnCl2 = (atomic mass of Zn) + 2 * (atomic mass of Cl)
The atomic masses of Zn and Cl are 65.38 g/mol and 35.45 g/mol respectively.
Molar mass of ZnCl2 = (65.38 g/mol) + 2 * (35.45 g/mol) = 136.28 g/mol
Now, we can calculate the number of moles of ZnCl2 formed:
moles = 68 g / 136.28 g/mol
moles = 0.5 mol
So, 0.5 moles of ZnCl2 formed.
Moving on to step 2:
Step 2: Calculate the percentage of purity of the sample.
We need to find the actual amount of Zn present in the sample in order to calculate the purity. We can use stoichiometry and the balanced equation to find the theoretical yield of Zn.
The balanced equation is: Zn + 2HCl -> ZnCl2 + H2
From the balanced equation, we can see that the molar ratio of Zn to ZnCl2 is 1:1.
So, the number of moles of Zn formed is also 0.5 moles.
Now, we can calculate the mass of Zn present in the sample:
mass = moles * molar mass
mass = 0.5 mol * 65.38 g/mol
mass = 32.69 g
The percentage of purity can be calculated as:
Percentage of purity = (Actual mass / Theoretical mass) * 100%
Percentage of purity = (32.69 g / 40.88 g) * 100%
Percentage of purity = 79.9%
Therefore, the sample has a purity of 79.9%.
Finally, let's move on to step 3:
Step 3: Calculate the concentration of HCl if 0.2 dm³ HCl reacted with Zn.
The balanced equation shows that the molar ratio of Zn to HCl is 1:2.
So, for every mole of Zn, 2 moles of HCl are required.
We already know that 0.5 moles of Zn reacted.
Therefore, the number of moles of HCl required is 2 * 0.5 moles = 1 mole.
We are given the volume of HCl as 0.2 dm³.
The concentration of HCl can be calculated using the formula:
Concentration = moles / volume
Concentration = 1 mol / 0.2 dm³
Concentration = 5 mol/dm³
Therefore, the concentration of HCl in the reaction is 5 mol/dm³.