Calculate the pH of a solution obtained by mixing 100cm3 of 0.1M HCl and 100cm3 of 0.2M NaOH
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To calculate the pH of a solution obtained by mixing 100 cm3 of 0.1 M HCl (hydrochloric acid) and 100 cm3 of 0.2 M NaOH (sodium hydroxide), we need to determine the final concentration of the resulting solution. To do this, we'll use the concept of stoichiometry and the balanced chemical equation for the reaction between HCl and NaOH.
The balanced chemical equation for this neutralization reaction is as follows:
HCl + NaOH → NaCl + H2O
According to the balanced equation, for every 1 mole of HCl, we need 1 mole of NaOH to completely react.
Given:
Volume of HCl solution (V1) = 100 cm3
Concentration of HCl (C1) = 0.1 M
Volume of NaOH solution (V2) = 100 cm3
Concentration of NaOH (C2) = 0.2 M
Step 1: Calculate moles of HCl and NaOH:
Moles of HCl (n1) = C1 * V1
= 0.1 M * 0.1 L
= 0.01 mol
Moles of NaOH (n2) = C2 * V2
= 0.2 M * 0.1 L
= 0.02 mol
Step 2: Determine the limiting reactant:
Since the stoichiometry of the reaction is 1:1 between HCl and NaOH, the limiting reactant will be the one with fewer moles. In this case, HCl has fewer moles (0.01 mol), so it is the limiting reactant.
Step 3: Calculate remaining moles of HCl after reaction:
Since HCl is the limiting reactant, all of it will react. Therefore, the moles of HCl remaining will be zero.
Step 4: Calculate moles of NaCl produced:
Since the stoichiometry of the reaction is 1:1 between HCl and NaCl, the moles of NaCl produced will be the same as the moles of HCl used, which is 0.01 mol.
Step 5: Calculate the volume of the resulting solution:
The total volume of the resulting solution is the sum of the volumes of HCl and NaOH used.
Volume of resulting solution = V1 + V2
= 0.1 L + 0.1 L
= 0.2 L
Step 6: Calculate the final concentration of the resulting solution:
The concentration of the resulting solution can be calculated by dividing the moles of NaCl by the volume of the resulting solution.
Concentration of resulting solution = Moles of NaCl / Volume of solution
= 0.01 mol / 0.2 L
= 0.05 M
Step 7: Calculate the pOH of the resulting solution:
pOH = -log10(C)
= -log10(0.05)
= 1.3
Step 8: Calculate the pH of the resulting solution:
Since pH + pOH = 14 (at 25°C), we can determine the pH by subtracting the pOH from 14.
pH = 14 - pOH
= 14 - 1.3
= 12.7
Therefore, the pH of the resulting solution obtained by mixing 100 cm3 of 0.1 M HCl and 100 cm3 of 0.2 M NaOH is approximately 12.7.