Q: What volume (in $\mu$L) of $0.125\ \mathrm{M}$ HBr contains $0.170$ moles HBr?

$21.25 \times 10^4\ \mu\mathrm{L}$

Question 1

Which of the following best describes molarity ($M$) in a solution?

Accepted Answer

The number of moles of solute per liter of solution.

Question 2

A patient with hypernatremia has a sodium ion concentration of $156\ \mathrm{mM}$ in $30.0\ \mathrm{mL}$ of blood. What mass (in mg) of sodium would be present? ($1\ \mathrm{mol\ Na^+} = 22.99\ \mathrm{g}$)

Accepted Answer

$4,950\ \mathrm{mg}$

Question 3

What is the molarity of a solution prepared by dissolving $2.37\ \mathrm{g}$ NaOH in enough water to make $2.50\ \mathrm{L}$ of solution? ($\mathrm{NaOH}$ molar mass $= 40.00\ \mathrm{g/mol}$)

Accepted Answer

$0.027\ \mathrm{M}$

Question 4

How many grams of Na$_3$PO$_4$ (MW: $163.94\ \mathrm{g/mol}$) are present in $300.0\ \mathrm{mL}$ of a $0.550\ \mathrm{M}$ Na$_3$PO$_4$ solution?

Accepted Answer

$27.1\ \mathrm{g}$

Question 5

A solution is prepared by dissolving $30.00\ \mathrm{mL}$ of benzene (C$_6$H$_6$, density $= 0.877\ \mathrm{g/mL}$) in dichloromethane to a final volume of $750.0\ \mathrm{mL}$. What is the molarity of benzene in the solution? (Molar mass of benzene $= 78.11\ \mathrm{g/mol}$)

Accepted Answer

$0.450\ \mathrm{M}$

Question 6

If $2.64\ \mathrm{g}$ of an unknown compound is dissolved in water to make $150.0\ \mathrm{mL}$ of solution with a concentration of $0.075\ \mathrm{M}$, what is the molecular weight of the compound?

Accepted Answer

$147\ \mathrm{g/mol}$

Question 7

What volume (in $\mu$L) of $0.125\ \mathrm{M}$ HBr contains $0.170$ moles HBr?

Accepted Answer

$21.25 	imes 10^4\ \mu\mathrm{L}$

Question 8

Which of the following is the correct formula for calculating molarity?

Accepted Answer

$\mathrm{Molarity} = \dfrac{\mathrm{moles\ solute}}{\mathrm{liters\ solution}}$

Question 9

A $5.8\ \mathrm{M}$ NaCl solution contains $58$ moles NaCl in what volume of solution?

Accepted Answer

$10.0\ \mathrm{L}$

Question 10

Which of the following best explains why conversion factors are important in molarity calculations?

Accepted Answer

They allow you to convert between units such as grams, moles, and liters to solve for unknowns.

Question 11

A solution is labeled as $0.250\ \mathrm{M}$ KCl. How many moles of KCl are present in $500.0\ \mathrm{mL}$ of this solution?

Accepted Answer

$0.125\ \mathrm{mol}$

Question 12

A nurse needs to prepare $250.0\ \mathrm{mL}$ of a $0.100\ \mathrm{M}$ NaCl solution. How many grams of NaCl (MW $= 58.44\ \mathrm{g/mol}$) are required?

Accepted Answer

$1.46\ \mathrm{g}$

Question 13

If $0.500\ \mathrm{mol}$ of glucose is dissolved to make $2.00\ \mathrm{L}$ of solution, what is the molarity?

Accepted Answer

$0.250\ \mathrm{M}$

Question 14

A $0.200\ \mathrm{M}$ solution of H$_2$SO$_4$ is prepared by diluting $50.0\ \mathrm{mL}$ of a stock solution. What was the molarity of the stock solution if the final volume is $250.0\ \mathrm{mL}$?

Accepted Answer

$1.00\ \mathrm{M}$

Question 15

Which of the following scenarios would most likely result in hypernatremia?

Accepted Answer

A patient loses a large amount of water but retains sodium.

Molarity and Solution Calculations in GOB Chemistry

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