CHEMISTRY - STOICHIOMETRY

Stoichiometry Practice Problems

  • 10 questions
  • Difficulty: Hard
  • Board: CAIE
  • Attempt online on the examination portal

Here are the first 3 questions. Click “View all questions” to see the complete assessment.

Q1.

An 8.40 g sample of magnesium contains 1.20 g of an inert impurity. The magnesium reacts completely with nitrogen and gains 2.80 g in mass. Using Ar values Mg = 24 and N = 14, what is the empirical formula of the magnesium nitride formed?

  1. A) MgN2
  2. B) MgN
  3. C) Mg2N3
  4. D) Mg3N2

Q2.

A 15.9 g sample of an oxide of element X is completely reduced, producing 11.1 g of X. Using Ar values X = 74 and O = 16, what is the empirical formula of the oxide?

  1. A) X2O3
  2. B) XO
  3. C) XO2
  4. D) X2O5

Q3.

A 10.40 g impure sample is 75.0% potassium by mass, with the remainder inert. The potassium reacts completely with chlorine and gains 7.10 g. Using Ar values K = 39 and Cl = 35.5, what is the empirical formula of the product?

  1. A) K2Cl
  2. B) KCl
  3. C) KCl2
  4. D) K2Cl3

Q4.

A 25.0 g sample containing a silver oxide and 1.8 g of inert material is heated until the oxide decomposes completely. The final solid has a mass of 23.4 g. Using Ar values Ag = 108 and O = 16, what is the empirical formula of the silver oxide?

  1. A) Ag2O3
  2. B) AgO
  3. C) AgO2
  4. D) Ag2O

Q5.

A 6.35 g sample of copper is heated with 15.875 g of iodine. After the reaction, 3.175 g of unreacted iodine is removed. Using Ar values Cu = 63.5 and I = 127, what is the empirical formula of the copper iodide formed?

  1. A) Cu2I
  2. B) Cu2I3
  3. C) CuI2
  4. D) CuI

Q6.

An impure phosphorus sample has a mass of 15.5 g, but only 40.0% of it is phosphorus. All the phosphorus reacts with oxygen, increasing the mass by 8.0 g. Using Ar values P = 31 and O = 16, what is the empirical formula of the oxide?

  1. A) P2O3
  2. B) PO2
  3. C) P4O6
  4. D) P2O5

Q7.

A mixture of 8.4 g of iron and 4.8 g of sulfur is heated. All the sulfur reacts, but 2.8 g of iron remains unreacted and is removed. Using Ar values Fe = 56 and S = 32, what is the empirical formula of the iron sulfide produced?

  1. A) Fe2S3
  2. B) FeS2
  3. C) FeS
  4. D) Fe3S2

Q8.

A 5.00 g alloy contains 80.0% of element Q by mass. All of Q is converted into 14.65 g of a pure chloride, which is separated from the other material. Using Ar values Q = 40 and Cl = 35.5, what is the empirical formula of the chloride?

  1. A) QCl
  2. B) QCl2
  3. C) Q2Cl3
  4. D) QCl3

Q9.

The figure shows balance readings from an experiment in which copper is heated in air until its mass becomes constant. Using Ar values Cu = 63.5 and O = 16, what is the empirical formula of the copper oxide?

Diagram for question 9: The figure shows balance readings from an experiment in which copper is heated in air until its mass becomes…
  1. A) Cu2O
  2. B) Cu2O3
  3. C) CuO2
  4. D) CuO

Q10.

The figure records the masses obtained when element Y is heated with excess bromine. Using the relative atomic masses stated in the figure, what is the empirical formula of the bromide formed?

Diagram for question 10: The figure records the masses obtained when element Y is heated with excess bromine. Using the relative…
  1. A) Y2Br3
  2. B) YBr2
  3. C) YBr
  4. D) Y3Br2

What this assessment covers

Concepts Tested

  • stoichiometry

Question Mix

  • Hard questions included

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