Question #78d59

1 Answer
Stefan V.
Nov 14, 2016

#"0.002271 moles K"_2"Cr"_2"O"_7#

Explanation:

By defition, a #"0.1885-M"# solution of potassium dichromate, #"K"_2"Cr"_2"O"_7#, contains #0.1885# moles of solute for every liter of solution.

Since you know that

#color(blue)(ul(color(black)("1 L" = 10^3"mL")))#

you can say that your solution will contain

#"0.1885 M K"_2"Cr"_2"O"_7 = ("0.1885 moles K"_2"Cr"_2"O"_7)/(10^3"mL solution")#

You can thus use the molarity of the solution as a conversion factor to take you from volume of solution to moles or vice versa.

In your case, you have

#12.05 color(red)(cancel(color(black)("mL"))) * ("0.1885 moles K"_2"Cr"_2"O"_7)/(10^3color(red)(cancel(color(black)("mL")))) = color(darkgreen)(ul(color(black)("0.002271 moles K"_2"Cr"_2"O"_7)))#

The answer is rounded to four sig figs.

Related questions
See all questions in Molarity
Impact of this question
1675 views around the world
You can reuse this answer
Creative Commons License