Question

Assuming your sample has a mass of 100 grams, find the empirical formula for the following molecular composition: 88.8% copper; 11.2% oxygen. (EXPLAIN IN DETAIL AND SHOW ALL CALCULATIONS)

Answer 1

Step 1.

Find mass of each component

88.8% of 100g = 88.8 g Cu

11.2 % of 100g = 11.2g O

Step. 2

Determine moles of each by dividing it with their atmoic mass

Cu atomic mass =63.546 g/mol

O atomic mass = 15.9994 g/mol

moles = mass / molar mass ,for Cu = 88.8 g / 63.546g/mol = 1.397 mol

O = 11.2g / 15.9994g/mol = 0.7000 mol

Step3.

divide the one with least no. of mole in all the obtained moles above

O has least no. of among these two

O = 0.7000 mol / 0.7000mol = 1

Cu = 1.397 mol / 0.7000 mol = 1.9957

if it is very close to any integer , write that next nearest integer = 1.9957 ~ = 2

Step.4

Write empirical formula,with Cu = 2 and O =1

Cu₂O