1.1.2 Basic Principles and Techniques (Expressions of Reagent Concentration) Flashcards
Molarity is moles per Kg solvent
Molality is moles per L of solution
T or F
F
Molarity = Moles/L
Molality = Moles/Kg
What is the formula for Molarity?
M = (g/L) / MW
MW = Molecular weight
IF g/dL is given, what is the formula?
M = ((g/dL) / MW) x 10
OR
M = ((g/dL) x 10)) / MW
Equivalent weights per L of Solutions
a. Normality
b. Nomality
c. Nomarity
a
Formula for Equivalent weights?
EW = MW / Valence
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
f
What is the formula for Normality?
N or Eq/L
=
(g/L) / EW
EW = Equivalent weight
Amount of solute per 100 total units of solution
a. Dilution
b. % v/w
c. % w/v
d. Normality
c
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
T
Expression of relative concentration
a. Dilution
b. Ratio
a
Amount of something relative to another
a. Dilution
b. Ratio
b
What is the formula for Dilution?
D = SV / TV
OR
D = SV / (SV + DV)
SV = Solute volume
DV = Diluent volume
TV = Total Volume
What is the Molarity of a 1L solution containing 72g of H2O
(H=1, O=16)
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
What is the Molarity of 0.234 mol of CoCl2 in 0.527 L of solution
0.444
Solution:
The Moles is already given just divide it by the solution
REMEMBER: M = Moles/L of solution
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
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
What is the Molarity of 2 moles of NaOH in a 100 mL solution?
20
Solution
CONVERT mL to L
100mL -> 0.1L
REMEMBER: M = Moles/L of solution
2/0.1 = 20
Normality is _________ or equal to molarity base on the __________
Greater than, Valence
If the valence is greater than 2, the Normality is __________ Molarity
Greater than
If the valence is 1, the Normality is __________ Molarity
equal to molarity
If Normality is given and you need to find Molarity, what is the formula?
a. N/V
b. N x V
a
If Molarity is given and you need to find Normality, what is the formula?
a. M/V
b. M x V
b
What is the Normality of 0.1381 M NaOH?
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
What is the Normality of 0.0521 M H3PO4
0.156 N
Solution:
Valence: 3
N : M x V
N : 0.0521 x 3 = 0.156 N
What is the normality of 24.5 g H2SO4 in a 100mL of solution? Molarity?
H = 1
S = 32
O = 16
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
What is the Molarity in a 9.5 Eq/L H2O2?
M = 4.75
Solution:
M = N/V
M = 9.5 / 2
M = 4.75
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?
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
What is the concentration of a 2L or ethanol are needed to prepare 600mL of 20% ethanol?
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%
How much H2O2 is needed to prepare 10mL of a 1:10 dilution? What is Diluent volume?
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
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?
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
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:
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
