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# 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?
1. $molarity={"moles of solute"}/{"moles of solvent"}$
2. $molarity={"moles of solvent"}/{"moles of solution"}$
3. Both (a) and (b)
4. $molarity={"moles of solute"}/{"moles of solution"}$
2.
Which of the following correctly represents the equation for parts per million?
1. $"parts per million" = {mass of solute}/{mass of solvent} xx 1000000$
2. $"parts per million" = {mass of solute}/{mass of solution} xx 1000000$
3. $"parts per million" = {mass of solvent}/{mass of solute} xx 1000000$
4. $"parts per million" = {mass of solvent}/{mass of solution} xx 1000000$
3.
What is the molarity of 138 g NaOH dissolved in 4000 mL of water?
1. 0.8625 M
2. 1.725 M
3. 3.45 M
4. 6.90 M
4.
What is the molarity of 6 moles of sodium chloride dissolved in 450 mL of solution?
1. 75 mol/L
2. 13.3 mol/L
3. 0.013 mol/L
4. 133.3 mol/L
5.
What is the molality of 75 g of $CaO$ dissolved in 1680 g of water?
1. 0.045 molal
2. 44.64 molal
3. 446.4 molal
4. 4.43 molal
6.
A 560-gram sample of solution contains 44 g of lithium chloride. What is the concentration in parts per million?
1. 78.571 ppm
2. 78571 ppm
3. 785.71 ppm
4. 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?
1. 25%
2. 32.3%
3. 3.1%
4. 31%
8.
What is the molality of 4 moles of potassium nitrate dissolved in 240 g of water?
1. 16.7 molal
2. 60 molal
3. 0.0167 molal
4. 1.67 molal
9.
32.5 g of hydrated oxalic acid is dissolved to get 1.5 $dm^3$ 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%        You need to be a HelpTeaching.com member to access free printables.