The Mole Concept Exam 2 and Problem Solutions

The Mole Concept Exam 2 and Problem Solutions

1. Find relation between number of molecules of given matters;

I. C2H2 that includes 2mol H atom

II. CH4 that includes N atoms (N is Avogadro number)

III. C3H4 that includes 1,5 N C atoms



1mol C2H4 includes 4mol H atom

?mol C2H4includes 2mol H atom


?=0,5mol C2H4


1mol CH4 includes 5N atom

?mol CH4 includes N atom


?=0,2mol CH4


1mol C3H4 includes 3N C atom

?mol C3H4 includes 1,5N C atom


?=0,5mol C3H4

Thus relation between them: I=III>II

2. Find relation between number of atoms of given matters.

I. 6 PH3 molecules

II. CO2 that includes 24N atom

III. 8mol O3



1 PH3 molecule contains 4 atoms

6 PH3 molecules contain ? atom


?=24 atoms


CO2 includes 24 N atoms.


1mol O3 contains 3N atoms

8mol O3 contain ?N atoms


?=24N atoms

3. Which one of the following statements is false for 0,5mol C2H6? (C=12, H=1 and take Avogadro Number=6x1023)

I. It is 15 g

II. It includes 3x1023 C2H6 molecules

III. It includes 1mol C atom

IV. It includes 4 atoms.

V. It includes 3 g H.


I. molar mass of C2H6=2.(12) + 6.(1)=30g/mol

1mol C2H6 is 30g/mol

0,5mol C2H6 is ?mol


?=15 g/mol I is true


1molC2H6 includes 6x1023 C2H6 molecules

0,5mol C2H6 includes ?C2H6 molecules


?=3x1023 C2H6 molecules II is true


1mol C2H6 includes 2mol C atoms

0,5mol C2H6 include ?mol C atoms


?=1mol C atom, III is true


1mol C2H6 includes 8N atoms

0,5mol C2H6 includes ?N atoms


?=4N atoms, IV is false.


1mol C2H6 includes 6g H

0,5mol C2H6 includes ?g H


?=3 g H  V is true

4. If, 8,4 g X element includes 9,03x1022 atoms and 0,1mol X2Y3 compound is 16g find atomic mass of Y element. (Avogadro number is 6,02x1023)


Mole of X element is ;


Atomic mass of X;


Molar mass of X2Y3compound;


We find atomic mass of Y by;

2.X + 3Y =160

2.(56) + 3(Y)=160

Y=16g/mol is atomic mass of Y.

5. Which ones of the following statements are true for 0,2mol C3H4 and 0,5mol C2H6 gas mixture? (C=12, H=1 and N=Avogadro Number)

I. Mass of mixture is 23 g.

II. It includes 1,6mol C atom.

III. It includes 0,7N molecule.


I. Molar mass of C3H4 =3.(12) + 4.(1)=40g/mol

1mol C3H4 is 40g

0,2mol C3H4 ?g


?=8g C3H4

Molar mass of C2H6=2.(12) + 6.(1)=30g/mol

1mol C2H6 is 30 g

0,5 mol C2H6 is ? g


?=15 g C2H6

Total mass of mixture is=8 + 15=23 g I is true


1mol C3H4 contains 3mol C atoms

0,2mol C3H4 contains ?mol C atoms


?=0,6mol C atoms

1mol C2H6 contains 2mol C atoms

0,5mol C2H6 contains ?mol Catoms


?=1mol C atom

Total umber of C atoms in mixture is=0,6 + 1=1,6mol C atoms. II is true.


0,2mol C3H4 + 0,5mol C2H6 = 0,7mol molecule

There are 0,7N molecule in 0,7 mol mixture, III is true.