Mass of beaker: 59 Mass of beaker and citric acid: 61 Mass of beaker and citric
ID: 889376 • Letter: M
Question
Mass of beaker: 59
Mass of beaker and citric acid: 61
Mass of beaker and citric acid (after cooling): 61.06 or 61.1
Volume of NaOH: 15mL
Syringe Reading, mL
Citric acid added, mL
pH
30
2
11.20
28
3
10.81
27
4
10.21
26
5
10.
25
6
9.58
24
7
8.35
22
9
7.02
20
11
6.72
19
12
6.68
18
13
6.39
17
14
6.12
16
15
5.77
15
16
5.72
14
17
5.66
13
18
5.22
Syringe Reading, mL
Citric acid added, mL
pH
30
1
11.24
29
2
10.78
28
3
10.48
27
4
10.12
26
5
9.92
25
6
9.82
24
7
7.96
23
8
7.46
21
10
6.83
19
11
6.75
18
12
6.65
17
13
6.21
16
14
5.82
15
15
5.63
14
16
5.42
Mass of citric acid: 2g
Moles of citric acid: 0.0104
(MW = 192.0 g/mol)
Molarity of citric acid: 0.104M
(volume of solution = 100 mL)
Trial 1 equivalence point: 10+7=17/2= 8.5
Trial 2 equivalence point:10+7=17/2=8.5
Molarity (Trial 1):
Molarity (Trial 2):
Average Molarity:
I need help calculating the molarity of the citric acid per trial, please help and show work.
Syringe Reading, mL
Citric acid added, mL
pH
30
2
11.20
28
3
10.81
27
4
10.21
26
5
10.
25
6
9.58
24
7
8.35
22
9
7.02
20
11
6.72
19
12
6.68
18
13
6.39
17
14
6.12
16
15
5.77
15
16
5.72
14
17
5.66
13
18
5.22
Explanation / Answer
we can calculate the molarity of citric acid from pH of the solution.
From pH of the solution we can calculate the H+ ion concentration.
since citric acid is a tribasic acid, we can divide the H+ ion concentration by 3 to get the molarity of citric acid after neutralization reaction with NaOH.
e.g: For 1st reading pH = 11.20
=> - log[H+] = 11.20
=> [H+] = 6.31x10-12 M
Hence citric acid concentration = [H+] / 3 = 2.10x10-12 M
After calculating the citric acid concentration for each reading we can take the average.
Note that here we have calculated the molarity of citric acid after the reaction.