9.7g ofamixture of KOH and KCL was to
disolve to make 1litre solution.20cm of this solution required 25.0cm of 0.12Molarity HCL acid for complete neutralization.calculate the percentage by mass of KCL.
NOTE: You mean 20 mL or 20 cc or 20 cm^3 and not 20 cm.
KOH + HCl ==> KCl + H2O
millimols HCl = mL x M = 25 mL x 0.12 M = ?
millimols KOH = millimols HCl
mols KOH = millimols/1000 = ?
grams KOH = mols KOH x molar mass KOH = ? g KOH in the 20 mL sample. How many grams KOH in the 1000 mL? That's grams KOH in 20 cc x (1000/20) = ?
grams KOH + grams KCl = 9.7 in the sample. You know g KOH, calculate grams KCl.
% KCl = (grams KCl/grams sample)*100 = ?
Post your work if you get stuck.
To calculate the percentage by mass of KCl in the mixture, we need to determine the moles of KCl and the total mass of the mixture.
1. Determine the moles of HCl used:
Since we know the molarity and volume of the HCl solution used, we can calculate the moles using the formula:
moles = molarity × volume
moles HCl = 0.12 M × 25.0 cm³
moles HCl = 0.12 mol/L × 0.0250 L (since 25.0 cm³ = 0.0250 L)
moles HCl = 0.003 moles
2. Determine the moles of KOH used:
Since HCl and KOH react in a 1:1 ratio, the moles of KOH used will be equal to the moles of HCl used:
moles KOH = 0.003 moles
3. Calculate the mass of KOH used:
Since we know the moles of KOH used, we can use the molar mass to calculate the mass:
mass KOH = moles KOH × molar mass KOH
The molar mass of KOH is 56.11 g/mol (39.10 g/mol for K + 16.00 g/mol for O + 1.01 g/mol for H).
mass KOH = 0.003 moles × 56.11 g/mol
mass KOH ≈ 0.168 g
4. Calculate the mass of KCl:
Since the mass of the mixture is 9.7 g and the mass of KOH is 0.168 g, we can calculate the mass of KCl by subtracting the mass of KOH from the total mass:
mass KCl = mass mixture - mass KOH
mass KCl = 9.7 g - 0.168 g
mass KCl ≈ 9.532 g
5. Calculate the percentage by mass of KCl:
Percentage by mass of KCl = (mass KCl / mass mixture) × 100
Percentage by mass of KCl = (9.532 g / 9.7 g) × 100
Percentage by mass of KCl ≈ 98.3%
Therefore, the percentage by mass of KCl in the mixture is approximately 98.3%.