Question 1
Some pure magnesium carbonate was added to 145. mL of 1.00 M HCl. When the reaction had finished, the solution was acidic. 25.0 mL of 0.500 M Na2CO3 solution was required to neutralize the excess acid. What mass of magnesium carbonate was originally used?
Question 2
A 25.00 mL sample of HCl was added to a 0.1996 g sample of CaCO3. All the CaCO3 reacted, leaving some excess HCl.
CaCO3 + 2HCl à CaCl2 + H2O + CO2
The excess HCl required 48.96 mL of a 0.01044 M barium hydroxide solution for complete neutralization.
2HCl + Ba(OH)2 à BaCl2 + 2H2O
What was the molarity of the original HCl?
Question 3
A chemist measured the amount of CaCO3 present in an antacid tablet. A tablet weighing 0.743 g was dissolved in 25.0 mL of 0.500 M HCl, and boiled to remove the CO2 gas. The chemical reaction is this:
CaCO3 + 2HCl à CaCl2 + CO2 + H2O
The amount of HCl added was more than enough to react with all of the calcium carbonate present in the tablet
The excess HCl was back-titrated with 0.1500 M NaOH, requiring 16.07 mL of the NaOH solution to reach the endpoint.
What is the mass percent of CaCO3 in the antacid tablet?
Question 4
A 0.3017 g sample of a diprotic acid (molar mass = 126.07 g/mol) was dissolved in water and titrated with a 37.26 mL sample of sodium hydroxide. A 24.05 mL sample of this sodium hydroxide was then used to react with 0.2506 g of an unknown acid, which has been determined to be monoprotic. What is the molar mass of the unknown acid?
Question 5
4.65 g of Co(OH)2 is dissolved in 500.0 mL of solution. 3.64 g of an unknown acid is dissolved in 250.0 mL of solution. 18.115 mL of the base is used to titrate 25.0 mL of the acid to its endpoint. Calculate the molar mass of the acid and identify it.