The Mole Concept Exam2 and Problem Solutions

The Mole Concept Exam2 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

Solution:

I.

1mol C2H4 includes 4mol H atom

?mol C2H4 includes 2mol H atom

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

?=0,5mol C2H4

II.

1mol CH4 includes 5N atom

?mol CH4 includes N atom

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

?=0,2mol CH4

III.

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

Solution:

I.

1 PH3 molecule contains 4 atoms

6 PH3 molecules contain ? atom

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

?=24 atoms

II.

CO2 includes 24 N atoms.

III.

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.

Solution:

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

II.

1mol C2H6 includes 6x1023 C2H6 molecules

0,5mol C2H6 includes ?C2H6 molecules

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

?=3x1023 C2H6 molecules II is true

III.

1mol C2H6 includes 2mol C atoms

0,5mol C2H6 include ?mol C atoms

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

?=1mol C atom, III is true

IV.

1mol C2H6 includes 8N atoms

0,5mol C2H6 includes ?N atoms

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

?=4N atoms, IV is false.

V.

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)

Solution:

Mole of X element is ;

nx=(9,03x1022)/(6,02x1023)=0,15mol

Atomic mass of X;

AX=8,4/0,15=56g/mol

Molar mass of X2Y3 compound;

MX2Y3=16/0,1=160g/mol

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.

Solution:

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

II.

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.

III.

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

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

 

 

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