1.1.2 Basic Principles and Techniques (Expressions of Reagent Concentration)

Question 1

Molarity is moles per Kg solvent

Molality is moles per L of solution

T or F

Answer 1

F

Molarity = Moles/L
Molality = Moles/Kg

Question 2

What is the formula for Molarity?

Answer 2

M = (g/L) / MW

MW = Molecular weight

Question 3

IF g/dL is given, what is the formula?

Answer 3

M = ((g/dL) / MW) x 10

OR

M = ((g/dL) x 10)) / MW

Question 4

Equivalent weights per L of Solutions

a. Normality
b. Nomality
c. Nomarity

Answer 4

a

Question 5

Formula for Equivalent weights?

Answer 5

EW = MW / Valence

Question 6

What is valence?

a. Number of Hydrogen
b. Number of hydroxyl (OH)
c. Number of electrons gain or loss (Charge)
d. Both a and c
f. All of the above

Answer 6

f

Question 7

What is the formula for Normality?

Answer 7

N or Eq/L

=

(g/L) / EW

EW = Equivalent weight

Question 8

Amount of solute per 100 total units of solution

a. Dilution
b. % v/w
c. % w/v
d. Normality

Answer 8

c

Question 9

If g/100mL = g/dL

IF Molarity is given
g/dL = (M x MW)/10

IF Normality is given
g/dL = (N x EW)/10

T or F

Answer 9

T

Question 10

Expression of relative concentration

a. Dilution
b. Ratio

Answer 10

a

Question 11

Amount of something relative to another

a. Dilution
b. Ratio

Answer 11

b

Question 12

What is the formula for Dilution?

Answer 12

D = SV / TV

OR

D = SV / (SV + DV)

SV = Solute volume
DV = Diluent volume
TV = Total Volume

Question 13

What is the Molarity of a 1L solution containing 72g of H2O
(H=1, O=16)

Answer 13

4

Solution:

Add the Molar mass:
H = 1 x 2 = 2
O = 16 x 1 = 16
16 + 2 = 18
MW = 18

(72g/L) / 18
= 4

Question 14

What is the Molarity of 0.234 mol of CoCl2 in 0.527 L of solution

Answer 14

0.444

Solution:

The Moles is already given just divide it by the solution
REMEMBER: M = Moles/L of solution

Question 15

What is the molarity of 20.54 g of Al(NO3)3 in 1575 mL of solution/

Al = 26.982
N = 14.007
O = 16.000

Answer 15

0.0612 / 6.1 x 10^-2

Solution:
Add the molar mass:
Al: 26.982 x 1 = 26.982
N: 14.007 x 3 = 42.021
O: 16.000 x 9 = 144
MW = 213.003

CONVERT mL to L

1575 -> 1.575

20.54/213.003 = 0.0964
0.0964/1.575

= 0.0612

Question 16

What is the Molarity of 2 moles of NaOH in a 100 mL solution?

Answer 16

20

Solution
CONVERT mL to L

100mL -> 0.1L

REMEMBER: M = Moles/L of solution

2/0.1 = 20

Question 17

Normality is _________ or equal to molarity base on the __________

Answer 17

Greater than, Valence

Question 18

If the valence is greater than 2, the Normality is __________ Molarity

Answer 18

Greater than

Question 19

If the valence is 1, the Normality is __________ Molarity

Answer 19

equal to molarity

Question 20

If Normality is given and you need to find Molarity, what is the formula?

a. N/V
b. N x V

Answer 20

a

Question 21

If Molarity is given and you need to find Normality, what is the formula?

a. M/V
b. M x V

Answer 21

b

Question 22

What is the Normality of 0.1381 M NaOH?

Answer 22

0.1381 Eq/L

Solution:

Remember that the valence is the number of hydrogen

H = 1

Since molarity is Given the formula will be:

N = M X V

This indicates that If the valence is 1, the Normality is EQUAL TO Molarity

Question 23

What is the Normality of 0.0521 M H3PO4

Answer 23

0.156 N

Solution:

Valence: 3

N : M x V
N : 0.0521 x 3 = 0.156 N

Question 24

What is the normality of 24.5 g H2SO4 in a 100mL of solution? Molarity?
H = 1
S = 32
O = 16

Answer 24

N = 5 Eq/L
M = 2.5 M

Solution:

Add the Molar Mass:
H = 1 x 2 = 2
S = 32 x 1 = 32
O = 16 x 4 = 64
MW = 98

Valence = 2

EW = MW/V
EW = 98/2
EW = 49

CONVERT mL to L
100mL -> 0.1L
g/L = 24.5 g / 0.1L
g/L = 245 g/L

N = (245 g/L) / 49
N = 5

M = N/V
M = 5/2
M = 2.5

Question 25

What is the Molarity in a 9.5 Eq/L H2O2?

Answer 25

M = 4.75

Solution:
M = N/V
M = 9.5 / 2
M = 4.75

Question 26

How many mL of 60% ethanol are needed to prepare 2L of 20% ethanol? How much Distilled water is needed for to reach the total volume?

Answer 26

Volume for 60% ethanol: 666.67 mL
Total volume: 1333.33 mL

Solution:

CONVERT L to mL
2L -> 2000mL

V1 = (C2 x V2)/C1
V1 = (20 x 2000) / 60
V1 = 666.67 mL

Total volume:
2000mL - 666.67
= 1333.33 mL

Question 27

What is the concentration of a 2L or ethanol are needed to prepare 600mL of 20% ethanol?

Answer 27

6%

Solution

CONVERT mL to L or Vice versa
600mL to 0.6 L
2L to 2000mL

C1 = (C2 x V2)/V1
C1 = (20 x 0.6) / 2
C1 = 6%

Question 28

How much H2O2 is needed to prepare 10mL of a 1:10 dilution? What is Diluent volume?

Answer 28

Solute: 1 mL
Diluent: 9mL

Solution:

Cross multiply:

(X/10mL) x (1/10)
= 10/10
= 1 mL

Total volume is 10 from 1:10
Diluent volume:
10mL - 1mL
= 9mL

Question 29

A mixture consists of 2 parts of Solution A and 8 parts of Solution B. How many mL of Solution A and B are needed to create 5000 mL of the mixture?

Answer 29

Sol A = 1000
Sol B = 4000

Solution:

Total volume of Solution:
2+8 = 10

Sol A:
2/10 = 0.2
0.2 x 5000mL = 1000mL

Sol B:
5000mL - 1000mL = 4000mL

Question 30

If 3mL of serum is mixed with 0.007L of saline determine the following:

Dilution:
Ratio of D to TV:
Ratio of S to D:
Ratio of TV to S:

Answer 30

Dilution: 3/10 (3:10)
Ratio of D (Diluent) to TV: 7/10 (7:10)
Ratio of Sample to Diluent: 3/7 (3:7)
Ratio of TV to Sample:10/3 (10:3)

Solution
CONVERT L to mL
0.007 = 7mL

Total volume: 3 + 7 = 10mL