Question

The number of moles of C₂H₅OH which will weigh 138g is ______

Answer 1

C₂H₅OH is the formula of ethanol.

The molecular mass of ethanol is =2 X molecular mass of Carbon(C)+ 5 X molecular mass of Hydrogen(H)+molecular mass of Oxygen(O)+ molecular mass of Hydrogen(H)

The molecular mass of ethanol is =2 X 12 + 5 X 1 + 16 + 1

= 24 + 5 + 16 + 1

= 46 g

Given mass of ethanol = 138 g

The number of moles of a substance is defined as the ratio of a given mass of a substance to the molar mass of the substance.

The number of moles of a substance= 138/46

= 3 moles

So, The number of moles of C₂H₅OH which will weigh 138g is 3 moles