3. A solution is made by dissolving 5.00 g of impure sodium hydroxide in water and making it up to 1.00dm3 of solution. 25.0 cm3 of this solution is neutralized by 30.0 cm3 of hydrochloric acid of concentration 0.102 mol/dm3.
a) Calculate the number of mole of HCl.
b) Calculate the number of sodium hydroxide.
c) Calculate the percentage purity of the sodium hydroxide
To answer these questions, we need to follow a step-by-step process. Here's how you can calculate the number of mole of HCl, the number of sodium hydroxide, and the percentage purity of the sodium hydroxide:
a) Calculate the number of moles of HCl:
To do this, we need to use the formula:
moles = concentration × volume
Given:
concentration of HCl = 0.102 mol/dm3
volume of HCl = 30.0 cm3
First, we convert the volume from cm3 to dm3:
30.0 cm3 = 30.0 / 1000 dm3 = 0.030 dm3
Now, we can calculate the number of moles of HCl:
moles of HCl = 0.102 mol/dm3 × 0.030 dm3 = 0.00306 moles
Therefore, the number of moles of HCl is 0.00306 moles.
b) Calculate the number of moles of sodium hydroxide (NaOH):
To find the number of moles of NaOH, we need to use the balanced chemical equation for the neutralization reaction between NaOH and HCl:
NaOH + HCl -> NaCl + H2O
The balanced equation tells us that one mole of NaOH reacts with one mole of HCl. So, the number of moles of NaOH is the same as the number of moles of HCl: 0.00306 moles.
c) Calculate the percentage purity of sodium hydroxide (NaOH):
To find the percentage purity, we need to determine the mass of pure NaOH in the solution. Given that 5.00 g of impure NaOH is dissolved in 1.00 dm3, the mass of pure NaOH can be calculated as follows:
mass of pure NaOH = (percentage purity / 100) × mass of impure NaOH
We need to know the percentage purity of the sodium hydroxide to calculate this. Once we have that information, we can substitute the values and calculate the result.
Note: If the percentage purity is not given, it is not possible to calculate the percentage purity using the information provided in the question.
Therefore, at this point, we cannot calculate the percentage purity of sodium hydroxide without knowing its value.
NaOH + HCl ==> NaCl + H2O
mols HCl = M x L = ?
mols NaOH = mols HCl (from the 1:1 coefficients in the balanced equation)
grams NaOH = mols NaoH x molar mass NaOH
% NaOH = (g NaOH/g sample)*100 = >