General chemistry practice exam with answers

A full practice exam covering molar mass, moles, concentration, pH, buffers, stoichiometry, limiting reagents and titration. Answer online and get it checked at once, or print it with or without worked answers. New exams with different numbers come with a free account.

8 questions · 46 points · about 70 minutes

1. Question 1

   4 points

   Task

   What is the mass of 0.4 mol of water (H₂O)? Atomic masses (g/mol): H 1.01 · O 16.00.

   Mass in g (2 decimal places)

   g

   Numbers like 12.5 or 0.025, with as many decimals as asked. Masses and amounts count within 1%, pH values within ±0.02.

   Check Hint

2. Question 2

   6 points

   Task

   Work out the pH of a solution of ammonium chloride (NH₄⁺, pKa = 9.25) with c = 0.5 mol/L. Use the weak acid approximation.

   pH (2 decimal places)

   Numbers like 12.5 or 0.025, with as many decimals as asked. Masses and amounts count within 1%, pH values within ±0.02.

   Check Hint

3. Question 3

   8 points

   Task

   Burning propane: C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O. You start with 90.8 g of C₃H₈ and 55.2 g of O₂, and isolate 36.4 g of CO₂. Atomic masses (g/mol): H 1.01 · C 12.01 · O 16.00.

   Which substance is the limiting reagent?

   C₃H₈O₂

   Theoretical mass of CO₂ in g (2 decimal places)

   g

   Yield in % (1 decimal place)

   %

   Numbers like 12.5 or 0.025, with as many decimals as asked. Masses and amounts count within 1%, pH values within ±0.02.

   Check Hint

4. Question 4

   4 points

   Task

   Work out the pH of nitric acid (HNO₃) with c = 0.002 mol/L (strong acid, fully dissociated).

   pH (2 decimal places)

   Numbers like 12.5 or 0.025, with as many decimals as asked. Masses and amounts count within 1%, pH values within ±0.02.

   Check Hint

5. Question 5

   6 points

   Task

   Burning hydrogen: 2 H₂ + O₂ → 2 H₂O. How much H₂O can at most be formed from 131.9 g of O₂? Atomic masses (g/mol): H 1.01 · O 16.00.

   Amount of O₂ in mol (4 decimal places)

   mol

   Mass of H₂O in g (2 decimal places)

   g

   Numbers like 12.5 or 0.025, with as many decimals as asked. Masses and amounts count within 1%, pH values within ±0.02.

   Check Hint

6. Question 6

   8 points

   Task

   20 mL of formic acid (c = 0.2 mol/L, pKa = 3.75) are titrated with sodium hydroxide (c = 0.2 mol/L). Work out the starting pH, the volume to the equivalence point and the pH at the half-equivalence point.

   Starting pH (2 decimal places)

   Volume of NaOH to the equivalence point in mL

   mL

   pH at the half-equivalence point (2 decimal places)

   Numbers like 12.5 or 0.025, with as many decimals as asked. Masses and amounts count within 1%, pH values within ±0.02.

   Check Hint

7. Question 7

   4 points

   Task

   From sodium hydroxide solution with c = 2.5 mol/L you need 1000 mL of solution with c = 0.25 mol/L. How many mL of the stock solution do you need?

   Volume of stock solution in mL (2 decimal places)

   mL

   Water to add in mL

   mL

   Numbers like 12.5 or 0.025, with as many decimals as asked. Masses and amounts count within 1%, pH values within ±0.02.

   Check Hint

8. Question 8

   6 points

   Task

   A carbonic acid/hydrogen carbonate buffer contains c(H₂CO₃) = 0.2 mol/L and c(HCO₃⁻) = 0.4 mol/L (pKa = 6.35). Work out the pH.

   pH (2 decimal places)

   Numbers like 12.5 or 0.025, with as many decimals as asked. Masses and amounts count within 1%, pH values within ±0.02.

   Check Hint

Practice exam from cleversphere.ch, free online with answers and new questions