AnswerCategory: ChemistryHow are the mole and mass calculated
admin Staff asked 4 months ago

How are the mole and mass calculated

How are the mole and mass calculated for a sample of copper and oxygen compound?

A sample of compound is made entirely from copper and oxygen with a total mass of 0.1431g. The mass of copper in the compound was found to be 0.1271g. I need help calculating these –

a. Number of moles of copper in the sample

b. Mass of oxygen in the sample

c. Number of moles of oxygen in the sample

d. Use the mole of ratio of copper to oxygen, round to the nearest whole number to determine both the formula and the molar mass of the compound

Thanks!

1 Answers
admin Staff answered 4 months ago

a. Mass of copper = 0.1271 g
Molar mass of an element = Atomic mass of that element
Therefore, molar mass of copper is 63.546 g/mol
So, the number of moles of copper present in the sample is:
= Mass of copper / Molar mass of copper
= (0.1271 / 63.546) mol of copper
= 0.0020 mol of copper
b. Mass of oxygen = Total mass of compound – Mass of copper
= (0.1431 – 0.1271) g
= 0.016 g
c. Mass of oxygen = 0.016 g
Molar mass of an element = Atomic mass of that element
Therefore, molar mass of oxygen is 15.9994 g/mol
So, the number of moles of oxygen present in the sample is:
= Mass of oxygen / Molar mass of oxygen
= (0.016 / 15.9994) mol of oxygen
= 0.0010 mol of oxygen
d. Molar ratio of copper to oxygen is:
= 0.0020 : 0.0010
= 2 : 1
Hence, the formula of the compound is Cu2O.
The molar mass of Cu2O is (63.546 * 2 + 15.9994) g/mol
= 143.09 g/mol