Calculate the pH of a solution obtained by mixing 100cm3 of 0.1M HCl and 100cm3 of 0.2M NaOH
To calculate the pH of a solution obtained by mixing an acid (HCl) and a base (NaOH), we need to determine the resulting concentration of the hydronium ion (H3O+) in the solution.
Step 1: Calculate the moles of HCl:
Moles of HCl = Concentration (M) × Volume (L)
Moles of HCl = 0.1 M × 0.1 L
Moles of HCl = 0.01 moles
Step 2: Calculate the moles of NaOH:
Moles of NaOH = Concentration (M) × Volume (L)
Moles of NaOH = 0.2 M × 0.1 L
Moles of NaOH = 0.02 moles
Step 3: Determine the limiting reactant:
HCl and NaOH react in a 1:1 ratio, so the limiting reactant is HCl since it has the lesser number of moles.
Step 4: Calculate the excess moles of the base (NaOH):
Excess moles of NaOH = Moles of NaOH - Moles of HCl
Excess moles of NaOH = 0.02 moles - 0.01 moles
Excess moles of NaOH = 0.01 moles
Step 5: Calculate the new volume of the solution:
The total volume of solution is the sum of the initial volumes of HCl and NaOH.
Total volume = 100 mL + 100 mL = 200 mL
Step 6: Calculate the concentration of the excess base (NaOH) in the final solution:
Concentration of excess base = Excess moles of NaOH / Total volume
Concentration of excess base = 0.01 moles / 0.2 L = 0.05 M
Step 7: Determine the concentration of the remaining acid (HCl) in the final solution:
Since all of the HCl has reacted with NaOH, there is no remaining HCl in the solution.
Step 8: Calculate the concentration of the hydronium ion (H3O+):
Since the excess base (NaOH) has reacted with the acid (HCl) in a 1:1 ratio, the concentration of the hydronium ion is equal to the concentration of the excess base.
Concentration of H3O+ = Concentration of excess base = 0.05 M
Step 9: Calculate the pH of the solution:
pH = -log[H3O+]
pH = -log(0.05)
pH ≈ 1.3
Therefore, the pH of the solution obtained by mixing 100 cm3 of 0.1M HCl and 100 cm3 of 0.2M NaOH is approximately 1.3.
To calculate the pH of the solution obtained by mixing 100 cm^3 of 0.1M HCl and 100 cm^3 of 0.2M NaOH, we need to understand the concept of neutralization reaction between an acid and a base.
When an acid and a base react, they undergo a neutralization reaction, where the acid donates a proton (H+) to the base, forming water and a salt. In this case, HCl is the acid, and NaOH is the base.
The balanced chemical equation for the reaction between HCl and NaOH is:
HCl + NaOH -> H2O + NaCl
In this reaction, 1 mole of HCl reacts with 1 mole of NaOH to produce 1 mole of water and 1 mole of NaCl.
First, let's calculate the number of moles of HCl and NaOH used in the mixture.
Number of moles of HCl = concentration of HCl * volume of HCl
= 0.1M * (100 cm^3 / 1000 cm^3/1 L)
= 0.01 moles
Number of moles of NaOH = concentration of NaOH * volume of NaOH
= 0.2M * (100 cm^3 / 1000 cm^3/1 L)
= 0.02 moles
Since the reaction is 1:1, the moles of HCl is equal to the moles of NaOH.
Therefore, all the HCl reacts completely with NaOH, leaving no excess HCl or NaOH in the solution.
Now, let's calculate the concentration of the resulting NaCl solution.
Total volume of the resulting solution = volume of HCl + volume of NaOH
= 100 cm^3 + 100 cm^3
= 200 cm^3
Concentration of NaCl = moles of NaCl / volume of NaCl solution
= 0.01 moles / (200 cm^3 / 1000 cm^3/1 L)
= 0.05 M
Now, we can calculate the pH of the resulting solution using the formula:
pH = -log10[H+]
Since NaCl is a salt that ionizes completely in water, it does not contribute to the pH of the solution. The concentration of H+ ions in the resulting solution is zero.
Therefore, the pH of the solution obtained by mixing 100 cm^3 of 0.1M HCl and 100 cm^3 of 0.2M NaOH is 7, which is neutral.