Introduction
 
Matters and Properties of Matters
 
Atomic Structure with Examples
 
Periodic Table
 
The Mole Concept with Examples
 
Gases with Examples
 
Chemical Reactions with Examples
 
Nuclear Chemistry (Radioactivity)
 
Solutions
 
Acids and Bases
 
Thermochemistry
 
Rates of Reactions (Chemical Kinetics)
 
Chemical Equilibrium
 
Chemical Bonds
 
Exams and Problem Solutions
 
--Matters and Properties of Matters Exams and Problem Solutions
 
--Atomic Structure Exams and Problem Solutions
 
--Periodic Table Exams and Problem Solutions
 
--The Mole Concept Exams and Problem Solutions
 
--The Mole Concept Exam1 and Problem Solutions
 
--The Mole Concept Exam2 and Problem Solutions
 
--Gases Exams and Problem Solutions
 
--Chemical Reactions Exams and Problem Solutions
 
--Nuclear Chemistry (Radioactivity) Exams and Problem Solutions
 
--Solutions Exams and Problem Solutions
 
--Acids and Bases Exams and Problem Solutions
 
--Thermochemistry Exams and Problem Solutions
 
--Rates of Reaction Exams and Problem Solutions
 
--Chemical Equilibrium Exams and Problem Solutions
 
--Chemical Bonds Exams and Problem Solutions
 
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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.

Solution:

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)

Solution:

C2H6=2.12+6.1=30

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)

Solution:

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)

Solution:

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.

Solution:

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

n=V/22,4

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

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

Solution:

We first find mole of O in the compound;

nO=(4,48x1023)/(6,02x1023)=0,8mol

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


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