Portage Learning CHEM 121 MODULE 2 EXAM 2025

Portage Learning CHEM 121 MODULE 2 EXAM




Portage Learning CHEM 121 MODULE 2 EXAM



Ques on 1

Number your answers, and show your work. Be sure to give answers with the correct units. Calculate the
molecular weight of the following compounds:

1. Ca3N2

2. Li3PO4

3. NH4NO3



Answer:

1. Ca3N2 = 3 (40.08) + 2 (14.01) = 148.26

2. Li3PO4 = 3 (6.941) + (30.97) + 4 (16.00) = 115.793

3. NH4NO3 = 2 (14.01) + 4 (1.008) + 3 (16.00) = 80.052



Ques on 2

Number your answers, and show your work. Be sure to give answers with the correct units. Calculate the
number of moles in 10.0 grams in the following compound:

1. NH4NO3



Calculate the number of grams in 0.0500 mol in the following compound: 2.
Li3PO4



Answer:

1. MW of NH4NO3 = 80.052 moles =

10..052 = 0.125 mole 2. MW of

Li3PO4 = 115.793 grams =


Portage Learning CHEM 121 MODULE 2 EXAM 2025

, Portage Learning CHEM 121 MODULE 2 EXAM




0.0500 x 115.793 = 5.79 grams



Ques on 3

Number your answers, and be sure to show your work. Calculate the % composi on of the following
compounds: 1. Na2SO4

2. Ca(NO3)2



Answer:

1. MW of Na2SO4 = 2 (22.99) + (32.07) + 4(16.00) = 142.05

%Na = 45..05 x 100 = 32.37%

%S = 32..05 x 100 = 22.58%

%O = 64..05 x 100 = 45.05%



2. MW of Ca(NO3)2 = (40.08) + 2 (14.01) + 6 (16.00) = 164.1

%Ca = 40..1 x 100 = 24.42%

%N = 28..1 x 100 = 17.07% %O
= 96..1 x 100 = 58.50%



Ques on 4

Number your answers, and be sure to show your work. Determine the empirical formula for the following
compound % composi ons:

1. 52.56% Fe, 2.83% H, 44.91% O

2. 71.98% C, 6.71% H, 21.31% O



Answer:

1) % Composi on of a compound is:


Portage Learning CHEM 121 MODULE 2 EXAM 2025