An aliquot containing 0.0004886 moles of Ca? is titrated to the Erlochrome Black
ID: 711346 • Letter: A
Question
An aliquot containing 0.0004886 moles of Ca? is titrated to the Erlochrome Black T end point. A blank containing a smal amount of measured Mg2+ requires 1.91 mL of EDTA to reach the end point. The aliquot to which the same amount of Mg2 is added requires 20.44 mL of EDTA solution to reach the end point. How many moles of EDTA are needed to titrate the Ca2+ in the aliquot? Express as a decimal number, not an exponent. Your Answer: Answer units Save Question 6 (10 points) An aliquot containing 0.0006936 moles of Ca? is titrated to the Eriochrome Black T end point. A blank containing a small amount of measured Mg2 requires 1.34 mL of EDTA to reach the end point. The aliquot to which the same amount of Mg2 is added requires 22.60 mL of EDTA solution to reach the end point. What is the molarity of the EDTA solution? Express as a decimal number, not an exponent. Your AnswerExplanation / Answer
Ca2+ ion and EDTA reacts 1:1 mole ratio.
So, the number of moles of EDTA required to titrate 0.0004886 moles of Ca2+ is 0.0004886 moles.
mL of EDTA consumed for Ca2+ ion = mL EDTA needed for sample - mL EDTA consumed for blank
= 20.44mL - 1.91 mL
= 18.53mL
Since 1 L = 1000 mL, 18.53 mL = 0.01853 L.
Molarity of EDTA = moles of EDTA/volume of EDTA
= 0.0004886 mol/0.01853 L
= 0.02636 mol/L
= 0.02636M.
Question 6:
Ca2+ ion and EDTA reacts 1:1 mole ratio.
So, the number of moles of EDTA required to titrate 0.0006936 moles of Ca2+ is 0.0006936 moles.
mL of EDTA consumed for Ca2+ ion = mL EDTA needed for sample - mL EDTA consumed for blank
= 22.60 mL - 1.34 mL
= 21.26 mL
Since 1 L = 1000 mL, 21.26 mL = 0.02126 L.
Molarity of EDTA = moles of EDTA/volume of EDTA
= 0.0006936 mol/0.02126 L
= 0.03262 mol/L
= 0.03262 M.
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