Question

A sample of chromium (III) carbonate dihydrate contains 2.34 x 10^24 atoms of chromium. How many grams of water does the same sample contain? Chromium is Cr on the periodic table.

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Answer 1

A sample of chromium (III) carbonate dihydrate contains 2.34 x 10^24 atoms of chromium. How many grams of water does the same sample contain?

mol of Cr = number of atoms of Cr / Avogadro’s number

= (2.34*10^24)/(6.022*10^23)

= 3.886 mol

chromium (III) carbonate dihydrate

Cr2(CO3)3.2H2O

1 mol of Cr2(CO3)3.2H2O has 2 mol of Cr

so,

number of mol of Cr2(CO3)3.2H2O = mol of Cr / 2

= 3.886 mol / 2

= 1.943 mol

Now,

1 mol of Cr2(CO3)3.2H2O has 2 mol of H2O

So,

mol of H2O = 2*number of mol of Cr2(CO3)3.2H2O

= 2*1.943 mol

= 3.886 mol

Answer: 3.886 mol