Question

Given the balanced equation for the oxidation of ethanol, C2H5OH, by potassium dichromate:

3 C2H5OH + 2 K2Cr2O7 + 16 HCl ---> 3 C2H4O2 + 4 CrCl3 + 4 KCl + 11 H2O
Calculate the volume of a 0.600M K2Cr2O7 solution needed to generate 0.1665 moles of C2H4O2 from a solution containing excess ethanol and HCl.

a) 278 mL b) 185 mL c) 111 mL d) 6.60 mL

Answer 1

The volume of a 0.600M K2Cr2O7 solution needed is 185 mL (option b)

Step-by-step explanation:

C₂H₅OH + 2 K₂Cr₂O₇ + 16 HCl ---> 3 C₂H₄O₂ + 4 CrCl₃ + 4 KCl + 11 H₂O

In the reaction ratio between dichromate and acetic, is 2:3, so 3 moles of acetic came from 2 moles of dichromate.

We want to know, how many moles of K₂Cr₂O₇, we used.

3 moles C₂H₄O₂ _______ 2 moles K₂Cr₂O₇

0.1665 moles C₂H₄O₂ _______ (0.1665 .2) / 3 = 0.111 moles

Solution of K₂Cr₂O₇ has a concentration of 0.6M

It means 0.6 moles in 1L of solution so, let's find the volume for 0.111 moles

0.6 moles are in 1 Liter

0.111 moles are in (0.111 .1)/0.6 = 0.185 L

0.185 L to mL = 185 mL