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
Solution:
I.
1mol C2H4 includes 4mol H atom
?mol C2H4includes 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.
1molC2H6 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 X2Y3compound;
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.