Q: A student is asked to prepare 250 mL of a 0.50 M NaCl solution. How many grams of NaCl (molar mass = 58.44 g/mol) are required?

$$\text{0.50 mol/L} \times 0.250\,\text{L} = 0.125\,\text{mol}$$; $$0.125\,\text{mol} \times 58.44\,\text{g/mol} = 7.305\,\text{g}$$

Q: A solution is prepared by dissolving 10.0 g of glucose (C$$_6H$_{12}O$_6$$, molar mass = 180.16 g/mol) in enough water to make 500 mL of solution. What is the molarity of the solution?

$$\frac{10.0\,\text{g}}{180.16\,\text{g/mol}} = 0.0555\,\text{mol}$$; $$M = \frac{0.0555\,\text{mol}}{0.500\,\text{L}} = 0.111\,M$$

Q: If you dilute 100 mL of a 2.0 M HCl solution to a final volume of 500 mL, what is the final concentration?

$$M_1V_1 = M_2V_2$$; $$2.0\,M \times 0.100\,L = M_2$ \times 0.500\,L$$; $$M_2 = 0.40$$\,M$$

Q: Which of the following is the correct setup to calculate the number of moles of solute in 350 mL of a 0.75 M solution?

$$\text{mol} = 0.75\,M \times 0.350\,L$$

Q: A nurse must prepare an IV solution by diluting 20 mL of a 5.0 M KCl stock solution to a final volume of 250 mL. What is the final concentration of KCl?

$$M_1V_1 = M_2V_2$$; $$5.0\,M \times 0.020\,L = M_2$ \times 0.250\,L$$; $$M_2 = 0.40$$\,M$$

Q: A chemist needs to make 1.0 L of a 0.10 M NaOH solution from a 2.0 M stock solution. What volume of stock solution is required?

$$M_1V_1 = M_2V_2$$; $$2.0\,M \times V_1$ = 0.10\,M \times 1.0\,L$$; $$V_1 = 0.050$$\,L = 50\,mL$$

Q: Which calculation would you use to determine the final concentration after mixing 100 mL of 1.0 M HCl with 400 mL of water?

$$M_1V_1 = M_2V_2$$; $$1.0\,M \times 0.100\,L = M_2$ \times 0.500\,L$$; $$M_2 = 0.20$$\,M$$

Q: A solution contains 0.25 mol of NaCl in 500 mL of solution. What is the molarity?

$$M = \frac{0.25\,\text{mol}}{0.500\,\text{L}} = 0.50\,M$$

Question 1

A student is asked to prepare 250 mL of a 0.50 M NaCl solution. How many grams of NaCl (molar mass = 58.44 g/mol) are required?

Accepted Answer

$$	ext{0.50 mol/L} 	imes 0.250\,	ext{L} = 0.125\,	ext{mol}$$; $$0.125\,	ext{mol} 	imes 58.44\,	ext{g/mol} = 7.305\,	ext{g}$$

Question 2

Which of the following best defines molarity ($$M$$)?

Accepted Answer

The number of moles of solute per liter of solution: $$M = \frac{	ext{mol solute}}{	ext{L solution}}$$

Question 3

A solution is prepared by dissolving 10.0 g of glucose (C$$_6H$_{12}O$_6$$, molar mass = 180.16 g/mol) in enough water to make 500 mL of solution. What is the molarity of the solution?

Accepted Answer

$$\frac{10.0\,	ext{g}}{180.16\,	ext{g/mol}} = 0.0555\,	ext{mol}$$; $$M = \frac{0.0555\,	ext{mol}}{0.500\,	ext{L}} = 0.111\,M$$

Question 4

If you dilute 100 mL of a 2.0 M HCl solution to a final volume of 500 mL, what is the final concentration?

Accepted Answer

$$M_1V_1 = M_2V_2$$; $$2.0\,M 	imes 0.100\,L = M_2$ 	imes 0.500\,L$$; $$M_2 = 0.40$$\,M$$

Question 5

Which of the following is the correct setup to calculate the number of moles of solute in 350 mL of a 0.75 M solution?

Accepted Answer

$$	ext{mol} = 0.75\,M 	imes 0.350\,L$$

Question 6

A nurse must prepare an IV solution by diluting 20 mL of a 5.0 M KCl stock solution to a final volume of 250 mL. What is the final concentration of KCl?

Accepted Answer

$$M_1V_1 = M_2V_2$$; $$5.0\,M 	imes 0.020\,L = M_2$ 	imes 0.250\,L$$; $$M_2 = 0.40$$\,M$$

Question 7

Which of the following statements about solution concentration is TRUE?

Accepted Answer

Diluting a solution decreases the concentration but does not change the amount of solute present.

Question 8

A chemist needs to make 1.0 L of a 0.10 M NaOH solution from a 2.0 M stock solution. What volume of stock solution is required?

Accepted Answer

$$M_1V_1 = M_2V_2$$; $$2.0\,M 	imes V_1$ = 0.10\,M 	imes 1.0\,L$$; $$V_1 = 0.050$$\,L = 50\,mL$$

Question 9

Which calculation would you use to determine the final concentration after mixing 100 mL of 1.0 M HCl with 400 mL of water?

Accepted Answer

$$M_1V_1 = M_2V_2$$; $$1.0\,M 	imes 0.100\,L = M_2$ 	imes 0.500\,L$$; $$M_2 = 0.20$$\,M$$

Question 10

A solution contains 0.25 mol of NaCl in 500 mL of solution. What is the molarity?

Accepted Answer

$$M = \frac{0.25\,	ext{mol}}{0.500\,	ext{L}} = 0.50\,M$$

Question 11

Which of the following best describes the process of preparing a solution of lower concentration from a stock solution?

Accepted Answer

Add a measured volume of stock solution to a volumetric flask, then add solvent until the desired final volume is reached.

Question 12

A laboratory technician needs to prepare 250 mL of 0.20 M MgCl$$_2$$ solution. How many grams of MgCl$$_2 ($$molar mass = 95.21 g/mol) are needed?

Accepted Answer

$$0.20\,M 	imes 0.250\,L = 0.050\,	ext{mol}$$; $$0.050\,	ext{mol} 	imes 95.21\,	ext{g/mol} = 4.76\,	ext{g}$$

Question 13

Which of the following is a correct application of the dilution equation $$M_1V_1 = M_2V_2$$?

Accepted Answer

To find the volume of stock solution needed to make a solution of lower concentration.

Question 14

A solution is labeled as 3.0 M H$$_2SO$_4. $$What does this mean?

Accepted Answer

There are 3.0 moles of H$$_2SO$_4$$ per liter of solution.

Question 15

A patient receives an IV containing 0.9% NaCl (w/v). What does this concentration mean?

Accepted Answer

There are 0.9 g of NaCl in every 100 mL of solution.

Terms, Units, and Dimensional Analysis in Chemistry

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