How many moles do you have if you weigh out 81.0 grams of cobalt(I) dichromate

n = 0,295 mol

Explanation:

I'm pretty sure there is no such thing as cobalt (I) dichromate, so I'm using cobalt (II) dichromate here.

To get the amount of substance, calculate the mass divided by the molar mass:

n = m / M

n = 81 g / 274,92 g/mol

n = 0,295 mol

89.7%

Explanation:

Percentage yield is the ratio of the actual yield of a product to the theoretical yield of a product  expressed as a percentage.

Percentage yield =  x 100

Given,

Actual yield of a product = 2.80 g

Theoretical yield of a product = 3.12 g

Percentage yield =  x 100 = 89.7 %