White Board Review

Practicing with Concentration Expressions

•Molarity•Percent•ppm

Determine the molarity of 250 mL of solution containing 35 g of NaOH.

mol soluteM =

L solution

What you must remember: molarity = moles of solute per liter of solution

1 mol NaOH

40.0 g NaOH

=

35 g NaOH

0.250 Liters

= 3.5 M NaOH

Practicing with Concentrations Molarity

What volume of a 2.0 M solution will provide 18 g of NaOH?

1.0 L

2.0 mol NaOH

What you must remember: moles solute ÷ molarity = L volume

1 mol NaOH

40.0 g NaOH

=18 g NaOH 0.45 mol NaOH

= 0.23 L0.45 mol NaOH

or 230 mL of solution

First find moles:

Next, divide moles by molarity:

Practicing with Concentrations Molarity

What mass of NaOH is needed to make 4.0 liters of a 0.75 M solution?

40.0 g NaOH

1 mol NaOH

What you must remember: L volume X molarity = moles solute

0.75 mol NaOH

L solution

=4.0 L solution 3.0 mol NaOH

=120 g NaOH3.0 mol NaOH

First find moles solute:

Next, multiply moles by molar mass:

Practicing with Concentrations Molarity

Determine the molarity of 850 mL of solution containing 95 g of KCl.

mol soluteM =

L solution

What you must remember: molarity = moles of solute per liter of solution

1 mol KCl

74.6 g KCl

=

95 g KCl

0.850 Liters

= 1.5 M KCl

Practicing with Concentrations Molarity

What volume of a 3.8 M solution will provide 120 g of LiF?

1.0 L

3.8 mol LiF

What you must remember: moles solute ÷ molarity = L volume

1 mol LiF

25.9 g LiF

=120 g LiF 4.63 mol LiF

= 1.2 L4.63 mol LiF

First find moles:

Next, divide moles by molarity:

Practicing with Concentrations Molarity

Practicing with Concentrations Molarity

What mass of NaSCN is needed to make 550 mL of a 2.4 M solution?

81.1 g NaSCN

1 mol NaSCN

What you must remember: L volume X molarity = moles solute

2.4 mol NaSCN

L solution

=0.55L solution 1.32 mol NaSCN

=110 g NaSCN1.32 mol NaSCN

First find moles solute:

Next, multiply moles by molar mass:

Determine the % w/v of 25 mL of solution containing 3.0 g of CsOH.

mv

2g solute% = 10

mL solution

What you must remember: % w/v = g of solute per mL of solution X 100

= 3.0 g CsOH

25 mL

= 12 % w/v CsOH

Practicing with Concentrations Percent

x 102

What volume of a 6.2 % w/v solution will provide 32 g of KMnO4?

What you must remember: g solute ÷ % w/v = mL volume

Practicing with Concentrations Percent

4

solution

6.2 g KMnO

100 mL

= 520 mL KMnO4 solution

First interpret % w/v: Next, divide the g solute by the %:

32 g4

solution100 mL

6.2 g KMnO

Practicing with Concentrations

What mass of NaClO is needed to make 150 mL of a 4.9 % w/v solution?

What you must remember: % w/v = g/100mL and mL volume X % = g solute

solution

4.9 g NaClO

100 mL

= 7.4 g NaClOX

First interpret % w/v: Next, multiply by mL volume:

Percent

150 mL

Determine the % w/v of 960 mL of solution containing 37 g of KClO3.

mv

2g solute% = 10

mL solution

What you must remember: % w/v = g of solute per mL of solution X 100

= 37 g KClO3

960 mL

= 3.9 % w/v KClO3

Practicing with Concentrations Percent

x 102

What volume of a 0.55 % w/v solution will provide 2.5 g of KNO2?

What you must remember: g solute ÷ % w/v = mL volume

Practicing with Concentrations Percent

2

solution

0.55 g KNO

100 mL

= 450 mL KNO2 solution

First interpret % w/v: Next, divide the g solute by the %:

2.5 g2

solution100 mL

0.55 g KNO

Practicing with Concentrations

What mass of NaSO4 is needed to make 500. mL of a 1.0 % w/v solution?

What you must remember: % w/v = g/100mL and mL volume X % = g solute

4

solution

1.0 g NaSO

100 mL

= 5.0 g NaSO4X

First interpret % w/v: Next, multiply by mL volume:

Percent

500. mL

Calculate the concentration in ppm of 3250mL of solution containing 0.25 g of NiSeO3.

6g soluteppm = 10

mL solution

What you must remember: ppm = g of solute per mL of solution X 106

= 0.25 g NiSeO3

3250 mL

= 77 ppm NiSeO3

Practicing with Concentrations ppm

x 106

What volume of a 320 ppm solution will provide 0.75 g of K2Cr2O7?

What you must remember: ppm = mg/L and mg solute ÷ ppm = L volume

Practicing with Concentrations

2 2 7

solution

320 mg K Cr O

1 L

= 750 mg

First interpret ppm: Next, convert g to mg:

0.75 g 1000 mg

1 g

ppm

Finally, divide mg solute by ppm:

750 mg2 2 7

solution1 L

320 mg K Cr O

= 2.3 L

Practicing with Concentrations

What mass of MgSO3 is needed to make 100. mL of a 38 ppm solution?

What you must remember: ppm = mg/L and L volume X ppm = mg solute

3

solution

38 mg MgSO

1 L

= 3.8 mg MgSO3X

First interpret ppm: Next, multiply by L volume:

0.100 L

ppm

Calculate the concentration in ppm of 25,000mL of solution containing 1.0 g of KF.

6g soluteppm = 10

mL solution

What you must remember: ppm = g of solute per mL of solution X 106

= 1.0 g KF

25,000 mL

= 40. ppm KF

Practicing with Concentrations ppm

x 106

What volume of a 5.0 ppm solution will provide 1.0 g of NaCN?

What you must remember: ppm = mg/L and mg solute ÷ ppm = L volume

Practicing with Concentrations

solution

5.0 mg NaCN

1 L

= 1000 mg

First interpret ppm: Next, convert g to mg:

1.0 g 1000 mg

1 g

ppm

Finally, divide mg solute by ppm:

1000 mgsolution1 L

5.0 mg NaCN

= 2.0 x 102 L

Practicing with Concentrations

What mass of FePO4 is needed to make 500. mL of a 120 ppm solution? What you must remember:

ppm = mg/L and L volume X ppm = mg solute

4

solution

120 mg FePO

1 L

= 60. mg FePO4X

First interpret ppm: Next, multiply by L volume:

0.500 L

ppm