Data: Titration with 0.0037M HCl with Varying Analytes Analyte Volume Analyte (m
ID: 1001741 • Letter: D
Question
Data: Titration with 0.0037M HCl with Varying Analytes
Analyte
Volume Analyte (mL)
Initial Burette Volume (mL)
Final Burette Volume (mL)
Volume Used (mL)
Mg(OH)2
50.0
0.00
9.52
9.52
Ca(OH)2
1.00
1.24
1.30
0.06
Sr(OH)2
0.50
0.00
18.48
18.48
Calculte and Compare to the Previous Experiments Values of:
Ksp Mg(OH)2 = 1.7E-11
Ksp Ca(OH)2 = 5.8E-5
Ksp Sr(OH)2 = 1.3E-3
Are the values similar?
Analyte
Volume Analyte (mL)
Initial Burette Volume (mL)
Final Burette Volume (mL)
Volume Used (mL)
Mg(OH)2
50.0
0.00
9.52
9.52
Ca(OH)2
1.00
1.24
1.30
0.06
Sr(OH)2
0.50
0.00
18.48
18.48
Explanation / Answer
From the given data we may calculate the concentration of Mg(OH)2, Ca(OH)2 and Sr(OH)2 .
1) The reaction will be
Mg(OH)2 + 2HCl --> MgCl2 + 2H2O
Moles of HCl reacted = Volume X molarity = 9.52 X 0.0037 = 0.0352 millimoles
Moles of Mg(OH)2 which must react = 1/2 X 0.0352 = 0.0176 millimoles
So concentration of Magnesium hydroxide = moles / Volume = 0.0176 / 50 = 0.000352
Mg(OH)2 --> Mg+2 + 2OH-
Each mole of Mg(OH)2 will give one mole of Mg+2 and 2 moles of OH-
so
Ksp = [Mg+2] [OH-]^2 = [0.000352][2X0.00352]^2 = 1.744 X 10^-10 ( a little less than the value of previous experiment)
2)the reaction will be
Ca(OH)2 + 2HCl --> CaCl2 + 2H2O
Moles of HCl reacted = Volume X molarity = 0.06 X 0.0037 = 0.000222 millimoles
Moles of Ca(OH)2 which must react = 1/2 X 0.000222 = 0.000111
So concentration of Calcium hydroxide = moles / Volume = 0.000111 / 1 = 0.000111
Ca(OH)2 --> Ca+2 + 2OH-
Each mole of Ca(OH)2 will give one mole of Ca+2 and 2 moles of OH-
so
Ksp = [Ca+2] [OH-]^2 = [0.000111][2X0.000111]^2 = 5.4 X 10^-12 (far different from previous value)
3) The reaction will be
Sr(OH)2 + 2HCl --> SrCl2 + 2H2O
Moles of HCl reacted = Volume X molarity = 18.58 X 0.0037 = 0.0687 millimoles
Moles of Sr(OH)2 which must react = 1/2 X 0.0687 = 0.0344 millimoles
So concentration of strontium hydroxide = moles / Volume = 0.0344 / 0.5 = 0.0687
Sr(OH)2 --> Sr+2 + 2OH-
Each mole of Sr(OH)2 will give one mole of Sr+2 and 2 moles of OH-
so
Ksp = [Sr+2] [OH-]^2 = [0.0687][2X0.0687]^2 = 1.3 X 10^-3 (same as previous value)
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