How many grams of silver chromate will precipitate when 150 mL of 0.500 M silver nitrate are added to 100 mL of 0.400 M potassium chromate?

1 Answer
Apr 23, 2017

WE need (i) a stoichiometric equation........and should get over 12*g12g of a brick-red precipitate.

Explanation:

2Ag^(+) + CrO_4^(2-) rarr Ag_2CrO_4(s)darr2Ag++CrO24Ag2CrO4(s)

Silver chromate is EXCEPTIONALLY insoluble, and will deposit with alacrity as a brick-red precipitate.

And we need equivalent quantities of silver ion and chromate ion.

"Moles of silver ion"=150xx10^-3*Lxx0.500*mol*L^-1=0.075*molMoles of silver ion=150×103L×0.500molL1=0.075mol

"Moles of chromate ion"=100xx10^-3*Lxx0.400*mol*L^-1=0.040*molMoles of chromate ion=100×103L×0.400molL1=0.040mol

Clearly, there is EXCESS chromate ion, MORE than 1/2 equiv. And thus all the silver ion will precipitate as silver chromate.

Given the stoichiometry, 0.075/2*mol0.0752mol Ag_2CrO_4Ag2CrO4 (approx. 12*g)12g) should precipitate......

i.e. 0.0375*molxx331.73*g*mol^-1=??*g0.0375mol×331.73gmol1=??g