Answer to Question #95059 in General Chemistry for Zabiba

Question

How many grams of the excess reagent remain assuming the reaction goes to completion and that you start with of Na2S and 12.1 g CuSO4?
Reaction: Na2S(aq) + CuSO4(aq) → Na2SO4(aq) + CuS(s

Answer 1

Molar mass of $Na_2S=78\ g\ mol^{-1}$

Molar mass of $CuSO_4=159.6\ g\ mol^{-1}$

Mass of $Na_2S\ taken= 8\ g\\$

Mass of $CuSO_4\ taken=12.1\ g$

Here $CuSO_4\ is\ the\ limiting\ reagent$

$159.6\ g\ copper\ sulphate\ react\ completely\ with\ 78\ g\ Na_2S$

So, $12.1\ g$ g $copper\ sulphate\ react \ with\ \frac{78}{159.6}\times12.1=5.9\ g\ Na_2S$

 excess reagent remain = $8-5.9=2.1\ g\ Na_2S$