If 25 cm^3 of the potassium hydroxide (KOH) solution was used to neutralise 35cm^3 hydrochloric (HCl)solution,
determine the concentration of the hydrochloric acid solution.
Thanks
What's the concn of the KOH?
mols HCl = M x L
mols KOH = mols HCl
M KOH = mols KOH/L KOH used.
To determine the concentration of hydrochloric acid solution, we need to use the concept of stoichiometry. When a base (KOH) reacts with an acid (HCl), they neutralize each other according to their balanced chemical equation.
The balanced chemical equation for the reaction between KOH and HCl is:
KOH + HCl -> KCl + H2O
From the balanced equation, we can see that one mole of HCl reacts with one mole of KOH to produce one mole of water.
Given:
Volume of KOH solution (V1) = 25 cm^3
Volume of HCl solution (V2) = 35 cm^3
To determine the concentration of HCl solution, we first need to calculate the number of moles of KOH and HCl used in the reaction.
Step 1: Calculate the number of moles of KOH:
The molar volume of a gas at standard temperature and pressure (STP) is 22.4 liters/mol. Since the volumes are in cm^3, we need to convert them to liters by dividing by 1000.
Using the formula: moles = volume (in liters) x concentration (in mol/l)
Volume of KOH solution (V1) = 25 cm^3
Concentration of KOH solution (C1) = unknown (to be determined)
moles of KOH = (25 cm^3 / 1000 cm^3/l) x C1 mol/l = (25/1000) x C1 mol = 0.025C1 mol
Step 2: Calculate the number of moles of HCl:
Using the same formula:
Volume of HCl solution (V2) = 35 cm^3
Concentration of HCl solution (C2) = unknown (to be determined)
moles of HCl = (35 cm^3 / 1000 cm^3/l) x C2 mol/l = (35/1000) x C2 mol = 0.035C2 mol
Step 3: Determine the stoichiometric relationship between KOH and HCl:
From the balanced equation, we know that the molar ratio between KOH to HCl is 1:1.
Therefore, the number of moles of KOH used (0.025C1 mol) is equal to the number of moles of HCl used (0.035C2 mol).
Step 4: Equate the moles of KOH and HCl used:
0.025C1 mol = 0.035C2 mol
Step 5: Solve for the concentration of HCl solution (C2):
Divide both sides of the equation by 0.035:
C1 = (0.025/0.035)C2
Simplify the equation:
C1 = 0.714C2
So, the concentration of the hydrochloric acid solution (C2) is approximately 1.4 times the concentration of the potassium hydroxide solution (C1).