AP®ChemistryCollege BoardExam QuestionsUnit 1: Atomic Structure & PropertiesElements & Mixtures

Elements & Mixtures (College Board AP® Chemistry): Exam Questions

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Elements & Mixtures

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11 mark

A scientist is examining a liquid mixture that contains water, ethanol, and dissolved sodium chloride. The mixture appears uniform to the eye and shows identical properties when analyzed in various parts.

Which of the following statements best describes this sample?

  • The sample is a homogeneous mixture because the components are mixed at the molecular level and are uniformly distributed.

  • The sample is a heterogeneous mixture because the dissolved sodium chloride forms distinct phases in the solution.

  • The sample is a pure substance because the components combine chemically to form a new formula unit.

  • The sample consists of distinct microscopic regions of water and ethanol that do not fully intermix, making it non-uniform at the molecular level.

Choose your answer

21 mark

Which of the following correctly identifies the molecular arrangement in a heterogeneous mixture?

  • All particles are identical and evenly spaced.

  • Different types of particles are evenly mixed at the molecular level.

  • Different types of particles are grouped into distinct regions.

  • The particles are chemically bonded, forming uniform molecular structures.

Choose your answer

11 mark

A compound contains a compound 39% sulfur, 58.6 % oxygen and the remainder is hydrogen. What is the empirical formula of the compound?

  • SOH

  • SO3H

  • SO3H2

  • S6O2H6

Choose your answer

21 mark

The chemical formula of the fertiliser ammonium nitrate is (NH4NO3). What is the mass of nitrogen in 23.15 g sample of ammonium nitrate?

  • 17.49g

  • 34.99g

  • 8.10 g

  • 4.05 g

Choose your answer

31 mark

Which masses of carbon and hydrogen respectively would be the same as the mass of carbon and hydrogen in a pure sample of butene, C4H8?

  • 48 g, 10 g

  • 60 g, 12 g

  • 84 g, 12 g

  • 72 g, 12 g

Choose your answer

41 mark

Consider the chemical compound H2S.

According to the Law of Definite Proportions, which of the following statements is true?

  • The mass ratio of hydrogen to oxygen in H2S can vary depending on the source of the compound.

  • The mass ratio of hydrogen to oxygen in H2S is always the same, regardless of the sample.

  • The mass ratio of hydrogen to oxygen in H2S is determined by the reaction conditions used to produce the compound.

  • The Law of Definite Proportions does not apply to the compound H2S.

Choose your answer

11 mark

A compound has the composition by mass:

H, 5.00%;    N, 35.00%;   O, 60.00%.

Which compound has this composition?

  • HNO3 

  • NH4NO3 

  • HNO2 

  • NH2OH

Choose your answer

21 mark

A 6.2 g sample of a mixture containing magnesium chloride and sodium bromide is found to contain 0.45 g of magnesium.

Assuming no other sources of magnesium in the sample, what is the mass percent of MgCl2 in the mixture?

  • 10.3%

  • 28.5%

  • 17.6%

  • 34.5%

Choose your answer

31 mark

A mixture of calcium carbonate and barium sulfate contains 30.0% of calcium carbonate.

If the mixture contains 1.20 g of calcium, what is the total mass of the mixture?

  • 4.00 g

  • 6.00 g

  • 9.99 g

  • 12.00 g

Choose your answer