1) A student measures 10.00ml of an unknown solution of fe2+ into a erlenmeyer f

Question

1) A student measures 10.00ml of an unknown solution of fe2+ into a erlenmeyer flask and diluted with 90.00ml of 1.0M hydrochloric acid. He then titrated this sample with the solution prepared in question #3( question 3 molarity of potassium dichromate = 0.001975moles/L) If 29.79ml of potassium dichromate solution is needed to reach the end point , what is the concentration of Fe2+ in the original unknown solution.

2) The balanced net ionic equation for the reaction of aqueous calcium chloride with aqueous sodium phosphate is.

3Ca 2+(aq) + 2 PO4 3- (aq)----> Ca3(PO4)2 (s)

a) what volume of 0.4312M calcium chloride solution would be needed to react completely with 18.00ml of 0.3610M sodium phospate solution???

b) what mass of calcium phosphate would be formed by this reaction??

Explanation / Answer

moles of dichromate solution used = 29.79*0.001975/1000 = 0.000058835 moles

therefore moles of Fe2+ used = 0.000058835

Molarity in 100ml of solution = 0.000058835/(100/1000) = 0.00058835M

molarity in 10ml solution = 0.0058835 M

2)

from the reaction

3 moles of Ca2+ = 2 moles of PO4 3- = 1 mole of Ca3(PO4)2

1 mole of PO4 3- = 1.5 * moles of Ca2+

18*0.3610 = 1.5*V(ml)*0.4312

v(ml) = 1.0046 ml

1 moles of PO4 3- = 0.5 mole of Ca3(PO4)2

moles of Ca3(PO4)2 formed = 2*18*0.3610/1000 = 0.012996 moles

weight of Ca3(PO4)2 = 0.012996*310 = 4.02876 gms

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.