# Calculations of Concentrations

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## Calculations of Concentrations Answer Key

1.

Which of the following correctly represents the equation for the molarity of a solution?

- [math]molarity={"moles of solute"}/{"moles of solvent"}[/math]
- [math]molarity={"moles of solvent"}/{"moles of solution"}[/math]
- Both (a) and (b)
- [math]molarity={"moles of solute"}/{"moles of solution"}[/math]

2.

Which of the following correctly represents the equation for parts per million?

- [math]"parts per million" = {mass of solute}/{mass of solvent} xx 1000000[/math]
- [math]"parts per million" = {mass of solute}/{mass of solution} xx 1000000[/math]
- [math]"parts per million" = {mass of solvent}/{mass of solute} xx 1000000[/math]
- [math]"parts per million" = {mass of solvent}/{mass of solution} xx 1000000[/math]

3.

What is the molarity of 138 g NaOH dissolved in 4000 mL of water?

- 0.8625 M
- 1.725 M
- 3.45 M
- 6.90 M

4.

What is the molarity of 6 moles of sodium chloride dissolved in 450 mL of solution?

- 75 mol/L
- 13.3 mol/L
- 0.013 mol/L
- 133.3 mol/L

5.

What is the molality of 75 g of [math]CaO[/math] dissolved in 1680 g of water?

- 0.045 molal
- 44.64 molal
- 446.4 molal
- 4.43 molal

6.

A 560-gram sample of solution contains 44 g of lithium chloride. What is the concentration in parts per million?

- 78.571 ppm
- 78571 ppm
- 785.71 ppm
- 7857.1 ppm

7.

A 620-gram sample of gas has 200 g of xenon. What is the percent composition of xenon in this gas sample?

- 25%
- 32.3%
- 3.1%
- 31%

8.

What is the molality of 4 moles of potassium nitrate dissolved in 240 g of water?

- 16.7 molal
- 60 molal
- 0.0167 molal
- 1.67 molal

9.

32.5 g of hydrated oxalic acid is dissolved to get 1.5 [math]dm^3[/math] of solution. Calculate the normality of the solution.

- 0.344 N

10.

A 597-g sample of a metal alloy contains 12.6 grams of copper. What is the percent composition of copper in this metal alloy?

- 2.11%

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