CALCULATIONS
Part A
molarity
𝑚
𝑚𝑚
2.0046𝑔
100.0869𝑔/𝑚𝑜𝑙
𝑛 =
𝑛 =
𝑀 =
𝑀 =
𝑛 = 0. 02002𝑚𝑜𝑙
𝑛
𝑉
0.02002𝑚𝑜𝑙
2
𝑀 = 0. 01001𝑀
Part C
Average Volume for Blank
1.7 + 0.9 + 0.6
3
= 1. 06𝑚𝐿
molarity of EDTA
𝑛
𝑉
0.02002𝑚𝑜𝑙
11.5𝑚𝐿
𝑀 =
𝑀 =
𝑛
𝑉
0.02002𝑚𝑜𝑙
11.53𝑚𝐿
𝑀 =
𝑀 =
𝑀 = 0. 00174𝑀
𝑀 =
𝑀 =
𝑀 = 0. 00174𝑀
𝑛
𝑉
0.02002𝑚𝑜𝑙
10.6𝑚𝐿
𝑀 = 0. 00189𝑀
average molarity of EDTA
0.00174𝑀 + 0.00174𝑀 + 0.00189𝑀
3
= 0. 00179𝑀
|0. 00174 − 0. 00179| = 0. 00005
|0. 00174 − 0. 00179| = 0. 00005
|0. 00189 − 0. 00179| = 0. 0001
0.00005 + 0.00005 + 0.0001
=
3
0.000067
* 100 = 3. 7
0.00179𝑀
0. 000067
Part D
moles
𝑛 =
𝑛 =
𝐶
𝑉
0.00174
25
𝑛 =
𝑛 =
−5
𝑛 = 6. 96 × 10
𝑛 =
𝑛 =
−5
𝑛 = 6. 96 × 10
weight of CaCO3 per 25mL
𝑚 = 𝑛 × 𝑚𝑚
−5
𝐶
𝑉
0.00174
25
𝑚 = (6. 96 × 10 ) × 100. 0869
𝑚 = 0. 00697𝑔
𝐶
𝑉
0.00189
25
−5
𝑛 = 7. 56 × 10
𝑚 = 𝑛 × 𝑚𝑚
−5
𝑚 = (7. 56 × 10 ) × 100. 0869
𝑚 = 0. 00757𝑔
Weight of CaCO3 per 106mL
6
𝑚𝑎𝑠𝑠
25.00𝑚𝐿
=
𝑚𝑎𝑠𝑠
25.00𝑚𝐿
× 10
0.00697𝑔
25.00𝑚𝐿
6
× 10
=
= 278. 8𝑔
6
𝑚𝑎𝑠𝑠
25.00𝑚𝐿
× 10
0.00697𝑔
25.00𝑚𝐿
6
× 10
= 278. 8𝑔
=
6
× 10
0.00757𝑔
25.00𝑚𝐿
6
× 10
= 302. 8𝑔
ppm of CaCO3
−5
=
−5
6.96 × 10
2
−5
−5
6.96 × 10
2
=
=
−5
= 3. 48 × 10
= 3. 48 × 10
average CaCO3
−5
3.48 ×10
|( 3. 48
|( 3. 48
|( 3. 48
−5
1.0×10
−5
+ 3.48 ×10
3
−5
−5
+ 3.48 ×10
−5
= 3. 58 × 10
−5
|
−5
× 10 )|
−5
× 10 )|
× 10 ) − ( 3. 58 × 10
−5
× 10 ) − ( 3. 58
−5
× 10 ) − ( 3. 78
−5
+ 1.0×10
3
−6
+ 3.0×10
−5
) = 1. 0 × 10
−5
= 1. 0 × 10
−6
= 3. 0 × 10
−5
= 2. 3 × 10
7.56 × 10
2
−5
= 3. 78 × 10
WRITTEN ANSWERS
1.
Equations and givens
𝑛 =
𝑚
𝑚𝑚
Calculations
𝑀=
𝑛
𝑉
𝑛 =
2.0046𝑔
100.0869𝑔/𝑚𝑜𝑙
𝑀 =
𝑛 = 0. 02002𝑚𝑜𝑙
0.02002𝑚𝑜𝑙
2
𝑀 = 0. 01001𝑀
mass = 2.0029g
molar mass [CaCO3] = 100.0869g/mol
equations and given
Calculations
Average volume of blank
1.7 + 0.9 + 0.6
3
Molarity of EDTA
𝑀 =
𝑀 =
𝑀 =
= 1. 06𝑚𝐿
𝑛
𝑛
𝑀 = 𝑉
𝑀
𝑉
0.02002𝑚𝑜𝑙
0.02002𝑚𝑜𝑙
𝑀 = 11.53𝑚𝐿
11.5𝑚𝐿
0.02002𝑚𝑜𝑙
10.6𝑚𝐿
=
𝑛
𝑉
𝑀 = 0. 00174𝑀
𝑀 = 0. 00174𝑀
𝑀 = 0. 00189𝑀
Average molarity of EDTA
0.00174𝑀 + 0.00174𝑀 + 0.00189𝑀
3
= 0. 00179𝑀
|0. 00174 − 0. 00179| = 0. 00005
|0. 00174 − 0. 00179| = 0. 00005
|0. 00189 − 0. 00179| = 0. 0001
0.00005 + 0.00005 + 0.0001
=
3
0.000067
* 100 = 3. 7
0.00179𝑀
Equations and given
Calculations
Moles of EDTA
𝑚
𝑛 = 𝑚𝑚
𝑀=
𝑛 =
𝑛
𝑉
𝑛 =
𝑀
𝑉
0.00174
25
𝑛 =
0.00174
25
−5
0. 000067
𝑛 =
0.00189
25
−5
𝑛 = 6. 96 × 10
𝑛 = 6. 96 × 10
−5
𝑛 = 7. 56 × 10
Weight per 25mL
𝑚 = 𝑛 × 𝑚𝑚
−5
𝑚 = (6. 96 × 10 ) × 100. 0869
−5
𝑚 = (7. 56 × 10 ) × 100. 0869
𝑚 = 0. 00697𝑔
𝑚 = 0. 00757𝑔
Weight per 106mL
𝑚𝑎𝑠𝑠
25.00𝑚𝐿
6
× 10
6
=
0.00697𝑔
25.00𝑚𝐿
× 10 =
=
0.00757𝑔
25.00𝑚𝐿
× 10
6
0.00697𝑔
25.00𝑚𝐿
× 10
6
= 278. 8𝑔
Ppm of CaCO3
= 278. 8𝑔
= 302. 8𝑔
−5
=
−5
6.96 × 10
2
−5
6.96 × 10
2
=
7.56 × 10
2
=
−5
= 3. 48 × 10
−5
= 3. 48 × 10
−5
= 3. 78 × 10
Average CaCO3
−5
3.48 ×10
|( 3. 48
|( 3. 48
|( 3. 48
−5
1.0×10
−5
+ 3.48 ×10
3
−5
−5
+ 3.48 ×10
−5
= 3. 58 × 10
−5
|
−5
× 10 )|
−5
× 10 )|
× 10 ) − ( 3. 58 × 10
−5
× 10 ) − ( 3. 58
−5
× 10 ) − ( 3. 78
−5
+ 1.0×10
3
−6
+ 3.0×10
−
) = 1. 0 × 10
−
= 1. 0 × 10
−
= 3. 0 × 10
−5
= 2. 3 × 10
2. According to the Guidelines for Canadian Drinking Water Quality, the degree of hardness for
drinking water can vary from in terms of calcium carbonate by which should be between 80
and 100 mg/L. Based on calculations in part D, the average content of calcium carbonate
present in unknown solution #1 is 3.77M. The solution is way lower than the acceptable water
hardness which means the solution needs to be diluted with distilled water.
𝑀1𝑉1 = 𝑀2𝑉2
𝑉1
𝑀2
2𝐿
3.77
𝑉2 =
=
=
2𝐿
3.77
𝑉2
𝑀1
𝑉2
100
× 100
𝑉2 = 52. 06
Therefore, about 52.06L of water should be added to soften up the water to reach about 100ppm.
3. The process of water softening is removing cations from water. Water softeners are ion
exchanges that remove mineral salts from hard water. Once these cations are removed, they
are placed in sodium ions. These exchanges usually happen within resin tanks. As the water
passes through these resin tanks and the minerals are replaced with sodium ions, salt content
is increased which results in softening the water. The regeneration process of softening water
comes in steps; backwash, brine draw, slow rinse, and fast rinse. During this process, the salt
water fills up the tank and the rinse cycle commences and washes the minerals off the beads.
It is then flushed out.
REFERENCES
Canada, H. (2009, February 13). Government of Canada. Canada.ca. Retrieved March 8, 2022,
from
https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadia
n-drinking-water-quality-guideline-technical-document-hardness.html