| Question 1: What volume of 0.09500 M sodium hydroxide is required to titrate a 10.00 mL sample of acetic acid (CH3COOH) that was made to a concentration of 0.1005 M? |
Answer to Question 1:
Write the balanced reaction
NaOH (aq) + CH3COOH (aq) 
NaCH3COO (aq) + H2O (l)
Read the question carefully. It tells us information about the base and the acid. It is really important not to mix up these information!
Information about the base, sodium hydroxide, NaOH:
- Volume = ? (We want to calculate this!)
- Concentration = 0.09500 M
Information about the nitric acid, CH3COOH:
- Volume = 10.00 mL
- Concentration = 0.1005 M
Let’s use the expanded roadmap to calculate the number of moles of the CH3COOH that is available.
(0.1005 moles/L CH3COOH)(0.01000 L CH3COOH) = 0.001005 mole of CH3COOH
The mole ratio of NaOH to CH3COOH is 1:1.
This tells us that it takes, 0.001005 mole of NaOH to neutralize the CH3COOH.
Using the expanded road map again, because we are given the concentration of the NaOH solution, we can calculate the volume of NaOH needed to neutralize the CH3COOH.
Since the concentration of the NaOH solution is 0.09500 M,
Volume of the NaOH = (0.001005 mole NaOH ) (1 L / 0.009500 mole) NaOH = 0.01057 L NaOH
| Question 2: A sample of battery acid is to be analyzed for its sulfuric acid content. A 1.00 mL sample of battery acid is diluted to 250.0 mL with water. A 10.00 mL sample of the diluted acid requires about 32.44 mL of 0.00986 M NaOH to complete the titration. What is the mass of sulfuric acid in the battery acid? |
Answer to Question 2:
This question involves a titration carried out on a dilute solution. The steps to this calculation are:
- Write the balanced equation
- Calculate the number of moles of H2SO4 in the 10.00 mL H2SO4
- Calculate the number of moles of H2SO4 in the 250.0 mL H2SO4
- Calculate the mass of H2SO4
Step 1 – Write the balanced equation
The balanced reaction is
2 NaOH (aq) + H2SO4 (aq) Na2SO4 (aq) + 2 H2O (l)
Step 2 – Calculate the number of moles of H2SO4 in the 10.00 mL H2SO4
Read the question carefully. It tells us information about the base and the acid. It is really important not to mix up these information!
Information about the base, sodium hydroxide, NaOH:
- Volume = 32.44 mL
- Concentration = 0.00986 M
Information about the sulfuric acid, H2SO4:
- Volume = 10.00 mL
Given, the volume of NaOH = 32.44 mL and the concentration of NaOH = 0.00986 M, let’s use the expanded roadmap to calculate the number of moles of sodium hydroxide, NaOH.
(0.00986 moles/L NaOH)(0.03244 L NaOH) = 0.0003199 mole of NaOH
From the balanced equation,
2 NaOH (aq) + 1 H2SO4 (aq) Na2SO4 (aq) + 2 H2O (l)
The mole ratio of NaOH to H2SO4 is 2:1.
Therefore, since 0.0003199 mole of NaOH is used to neutralize the H2SO4, there must have been 0.0003199 mole /2 = 0.0001599 moles of H2SO4 in the 10.00 mL H2SO4.
Step 3 – Calculate the number of moles of H2SO4 in the 250.0 mL of H2SO4
Multiply Step 2 by 25 since 250.0 mL / 10.00 mL = 25.
(0.0001599 moles)(25.0) = 0.0039975 moles H2SO4
Step 4 – Calculate the mass of H2SO4
The molar mass of H2SO4 = 98.078 g / mole
(0.0039975 moles H2SO4)·(98.078 g / mole H2SO4) = 0.392 g H2SO4
