**ANSWERS TO PRACTICE PROBLEMS:**

1.
IF YOU HAVE WEIGHED 90 GRAMS OF NAOH AND
DISSOLVED IT 1,500 ML OF WATER, WHAT IS THE;

A.
PERCENTAGE

% =

__Weight in grams X 100__
Total Volume in mL

% =

__90 x 100__
1,500

**% = 6 % of NaOH solution**

B.
MOLARITY

M=

__W in grams____MW__

Liter of solution

M =

__90____40__

1.5

**M = 1.5 M NaOH**

C.
NORMALITY

N= Mv

N = 1.5 X 1

**N = 1.5 N NaOH**

2.
HOW MANY GRAMS DO YOU NEED TO PREPARE 2M OF
NACL?

W = DM X DV X MW

W = 2 X 1 X 58.5

**W = 117 grams of NaCl**

How: weigh 117 grams of NaCl and dilute it
with DH20 up to the 1 Liter mark in a volumetric flask or measure 500 mL of
DH2O into a volumetric flask, weigh 117 grams of NaCl and dissolve. Add DH20 up
to 1 liter mark.

3.
HOW WOULD YOU PREPARE 1N OF HCL?

C1V1 = C2V2

C1= 12 N (Concentrated HCl)

C2 = 1N

V2 = 100 mL (assumption when no volume is
given)

V1 = unknown

V1 =

__C2V2__
C1

**V1 = 8.33 mL**

**How: Add 8.33 mL of concentrated HCl to 91.67 mL of DH2O.**

4.
HOW WOULD YOU PREPARE 0.85% NACL SOLUTION?

W =

__% X TV (total volume)__
100

W =

__0.85 X 100__(if no volumes are given assume that TV is 100)
100

**W = 0.85 g (grams) of NaCl**

How: Measure 50 mL of DH2O into a
volumetric flask. Weigh 0.85 grams of NaCl and dissolve completely. Add DH2O up
to the 100 mL mark.

5.
WHAT IS THE NORMALITY OF A 0.5 M CACL2 SOLUTION?

N = M X v (factor)

N = 0.5 X 2

**N = 1 N CaCl2**

6.
HOW DO YOU PREPARE A 1:10 SERUM DILUTION?

When no volume is given assume that 1 mL is
one part; hence,

1 mL = 1 part of solute

9 mL

__= 9 parts of diluent__
10 parts (total)

**Hence: dilution is 1:10**

How: Add 1 mL of serum to 9 mL of NSS to
come up with a 1:10 serum dilution.

7.
MAKE UP 500 ML OF 5M SOLUTION OF HCL

C1V1 = C2V2

V1 =

__C2V2__
C1

Before you substitute be sure that all your
units are the same. It does not matter what units you used as long as they are
similar units. i.e. if you use liters for volume all volumes should be
expressed in liters.

V1 =

__5 M X 500 mL__
12 (12 is standard Normal concentration of concentrated HCl, since
valence is 1, N=M.)

**V1 = 208.33 mL**

How: Add

**208.33 mL to 291.67 of DH2O**to produce 500 mL of 5M HCl solution.
8.
PREPARE THE FOLLOWING WORKING STANDARD SOLUTIONS FROM A STOCK SOLUTION OF 20 MG/DL:
STATE VOLUME OF DILUENT AND DILUTION.

A.
15 MG/DL

C1V1 = C2V2

V1 =

__C2V2__
C1

V1 =

__15 mg/Dl X 100 mL__
20 mg/dL

**V1 = 75 mL**

**75 mL of**20 mg/dL stock solution added to

**25 mL**of DH2O
B.
10 MG/DL

C1V1 = C2V2

V1 =

__C2V2__
C1

V1 =

__10 mg/Dl X 100 mL__
20 mg/dL

**V1 = 50 mL of 20 mg/dL stock solution added to 50 mL of DH2O**

C.
5 MG/DL

C1V1 = C2V2

V1 =

__C2V2__
C1

V1 =

__5 mg/Dl X 100 mL__
20 mg/dL

**V1 = 25 mL of 20 mg/dL stock solution added to 75 mL of DH2O**

D.
2 MG/DL

C1V1 = C2V2

V1 =

__C2V2__
C1

V1 =

__2 mg/Dl X 100 mL__
20 mg/dL

**V1 = 10 mL of 20 mg/dL stock solution added to 90 mL of DH2O**

**Volume of stock solution, diluent and dilution are the following:**

Volume of stock solution |
Volume of Diluent (DH2O) |
Dilution |

75 mL |
25 mL |
1:4 (diluent to solute) |

50 mL |
50 mL |
1:2 |

25 mL |
75 mL |
1:4 |

10 mL |
90 mL |
1:9 |

**1.**

**75 divided by 25 = 3 + 1= 4, hence dilution is 1:4 (diluent to solute)**

**2.**

**50 divided by 50 = 1 + 1= 2, hence dilution is 1:2**

**3.**

**75 divided by 25 = 3 + 1= 4 hence dilution is 1:4**

**4.**

**90 divided by 10 = 8 + 1 = 9, hence dilution is 1:9**

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