Module 3.1 Molecular Weight

Question 1

What is the Molecular Weight of

Ca₃(PO₄)₂

Answer 1

First layout the number of atoms
3 Ca
2 P
8 O
Then multiply by the mass (periodic table)
3 Ca * 40.08 = 120.24
2 P * 30.97 = 61.94
8 O * 16 = 128

Add together 120.24+61.94+128= 310.18

Question 2

What is the Molecular Weight of

C₃H₅O₂Cl

Answer 2

Layout each one
3 C
5 H
2 O
1 Cl
Find mass on periodic table & multiply
3 C * 12.01 = 36.03
5 H * 1.008 = 5.04
2 O * 16 = 32
1 Cl * 35.45 = 36.45

Add together
36.03+5.04+32+36.45= 108.52

Question 3

What is the Molecular Weight of

Al₂(SO₄)₃

Answer 3

First layout
2 Al
3 S
12 O
Find mass on periodic table and multiply 
2 Al * 26.98 = 53.96
3 S * 32.06 = 96.18
12 O * 16 = 192

And together
53.96+96.18+192= 342.14