The Mole Concept Exam1 and Problem Solutions

The Mole Concept Exam1 and  Problem Solutions


1. If atomic mass of Mg atom is 24 g, find mass of 1 Mg atom.


We can solve this problem in to ways;

1st way:

6,02x1023 amu is 1 g

24  amu           is ? g


?=4x10-23 g

2nd way;

1 mol Mg (6,02x1023 Mg atoms) is 24 g

6,02x1023 Mg atoms   24 g

1              Mg atom     ? g


?=4x10-23 g


2. Find mass of 1 molecule C2H6. (C=12, H=1)



6,02x1023 C2H6 molecule is 30 g

1              C2H6 molecule is ? g


1 C2H6 molecule is =?=5.10-23 g


3. Find mole of 6,9 g Na. (Na=23)


23 is the atomic mass of Na, in other words 1 mole Na is 23 g.

23 g Na is 1 mol

6,9 g Na is ? mol


?=0,3 mol


4. Find mass of 0,2 mol P4 . (P=31)


Molecule mass of P4 =4.31=124 g

1 mol P4 is 124 g

0,2 mol P4 is ? mol


?= 24,8 g


5. Find mole of 4,48 liters O2 under normal conditions.


Under normal conditions, 1 mol gas is 22,4 liters. We use following formula to find moles of gas under normal conditions;


n=4,48/22,4=0,2 mol


6. Find mass of Fe in the compound including 4,8x1023 O atoms ;Fe3O4 .


We first find mole of O in the compound;


Now we find mole of compound that contains 0,8mol O;

nFe3O4=(moles of O)/(moles of O in compound)=0,8/4=0,2mol

Mole of Fe in compound is;

There are 3 mol Fe in 1 mol Compound

there are ? mol Fe in 0,2mol compound


?=0,6 mol Fe in compound

mass of 0,6 mol Fe is;

1 mol Fe is 56 g

0,6 mol Fe is ? g


?=33,6g There are 33,6 g Fe in compound



Find Mass Of 02 Mol P4 (P=31)
Find the mass of 02 mol of P4