MCAS Chemistry Exam Practice - Question List

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36. Which of the following statements describes a difference between a mixture and a pure substance?

A mixture tends to be homogenous, while a pure substance tends to be heterogeneous.
A mixture has a specific melting point, while the melting point
of a pure substance can vary.
The density of a mixture can change with temperature, but the density of a pure substance cannot change.
The composition of a mixture can vary from sample to sample, but the composition of a pure substance is always the same.

37. Which of the following pieces of evidence best supports Bohr’s idea that electrons occupy specific energy levels within an atom?

Sodium atoms become positive ions when they lose electrons.
Each element emits a unique brightline spectrum when it falls from an excited state to a ground state.
Beryllium atoms bombarded with alpha particles produce beams that are not influenced by magnetic fields.
Each element has physical and chemical properties that are unique to that element and different from those of other elements.

38. The air inside a beach ball is at a temperature of 25°C and a pressure of 1.0 atm. If the ball contains 0.85 mol of air, what is its volume?

39. Which of the following correctly pairs a phase of matter with its description?

Solid: Particles have no motion.
Liquid: Particles expand to fill any container in which they are placed.
Gas: Particles have higher amounts of energy than when in the liquid phase.
Liquid: Particles are more strongly attached to one another than when in the solid phase.

40. Which of the following sections of the periodic table contains only metals?