1 tonne of CuSO4 contains how many kg of copper? (Mr; Cu=63.5, S=32, O=16)

Options
a) 63.5/159.5 * 1000 b) 63.5/96 * 1000 c) 63.5/159.5 * 1 d) 63.5/159.5 * 1/1000

1 Answer
Ernest Z.
Feb 7, 2018

a) #63.5/159.5 × 1000#

Explanation:

Let's look at the formula of copper(II) sulfate.#.

#A_text(r) = 63.5 color(white)(mll)32 color(white)(mm)16#
#color(blue)(color(white)(mmml)"Cu"color(white)(mm)"S"color(white)(mml)"O"_4)#
#M_text(r) = "63.5 + 32 + 4×16 = 159.5"#

The formula tells you that there are 63.5 units of copper in 159.5 units of #"CuSO"_4#

The units can be anything you want.

We usually use grams, but they could be micrograms, kilograms, tonnes, pounds, etc.

Thus, in 1 t of #"CuSO"_4# you have

#"Mass of Cu" = 1000 color(red)(cancel(color(black)("kg CuSO"_4))) ×"63.5 kg Cu"/(159.5color(red)(cancel(color(black)("kg CuSO"_4)))) = "398 kg Cu"#

Thus the numbers in the calculation are #1000 ×63.5/159.5#.

This question is an excellent example of why you should always use units in your calculations.

If the units don't cancel correctly, you know you have done something wrong.

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