Question 1

Three liquids are mixed together and placed into a flask. Which separation technique would be best for separating this mixture into its individual components, and which physical property does this technique rely on?

Accepted Answer

Distillation; relies on differences in boiling points

Question 2

An alloy is found to be 21% gold ($$\rho = 19.3 \ \mathrm{g/cm^3$}) $$and the rest silver ($$\rho = 10.5 \ \mathrm{g/cm^3$}). $$What is the density of the alloy? (Assume additive volumes.)

Accepted Answer

$$12.35 \ \mathrm{g/cm^3$}$$

Question 3

A student finds an irregularly shaped piece of metal with a mass of $$127.8 \ \mathrm{g}. $$When placed in $$40.0 \ \mathrm{mL} of $$water, the water level rises to $$51.3 \ \mathrm{mL}. $$What is the density of the metal?

Accepted Answer

$$11.2 \ \mathrm{g/cm^3$}$$

Question 4

Find the volume of an object with a mass of $$271 \ \mathrm{g}$$ and a density of $$7.15 \ \mathrm{g/cm^3$}.$$

Accepted Answer

$$37.9 \ \mathrm{cm^3$}$$

Question 5

Which of the following best explains why distillation can separate a mixture of liquids?

Accepted Answer

Because each liquid has a different boiling point

Question 6

A student needs to separate a mixture of sand and salt. Which method should they use and why?

Accepted Answer

Dissolve in water, filter, then evaporate; sand is insoluble, salt is soluble

Question 7

If a metal sample has a density closest to $$11.2 \ \mathrm{g/cm^3$}$$, which of the following is it most likely to be?

Accepted Answer

Lead ($$\rho = 11.2 \ \mathrm{g/cm^3$})$$

Question 8

A $$50.0 \ \mathrm{g}$$ sample of a substance is placed in a graduated cylinder containing $$30.0 \ \mathrm{mL} of $$water. The water level rises to $$36.5 \ \mathrm{mL}. $$What is the density of the substance?

Accepted Answer

$$7.69 \ \mathrm{g/cm^3$}$$

Question 9

Which of the following is NOT a physical property used to separate mixtures?

Accepted Answer

Radioactivity

Question 10

A student has a $$100 \ \mathrm{g}$$ sample of an unknown metal. When placed in water, the volume increases by $$8.93 \ \mathrm{mL}. $$What is the density of the metal, and which metal is it most likely to be from the following: Au ($$19.3 \ \mathrm{g/cm^3$}$$), Ag ($$10.5 \ \mathrm{g/cm^3$}$$), Cu ($$8.96 \ \mathrm{g/cm^3$}$$), Pb ($$11.2 \ \mathrm{g/cm^3$}$$)?

Accepted Answer

Density: $$11.2 \ \mathrm{g/cm^3$}$$; Metal: Pb

Question 11

Which of the following best describes why filtration cannot be used to separate a saltwater solution?

Accepted Answer

Salt is dissolved in water and passes through the filter

Question 12

A mixture contains three liquids with boiling points of $$60^\circ \mathrm{C}$$, $$80^\circ \mathrm{C}$$, and $$120^\circ \mathrm{C}. $$Which technique would best separate them and in what order would they be collected?

Accepted Answer

Distillation; $$60^\circ \mathrm{C}$$ first, then $$80^\circ \mathrm{C}$$, then $$120^\circ \mathrm{C}$$

General Chemistry Study Guide: Mixtures, Density, and Alloys

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