Question

Use the periodic table to calculate the molar mass of each compound below. Give your answer to the correct number of significant figures. Sodium hydroxide (NaOH): 2 g/mol Water (H2O): 4 g/mol Glucose (C6H12O6): 2 g/mol Calcium sulfate (CaSO4): 1 g/mol Magnesium phosphate (Mg3(PO4)2): 1 g/mol

Answer 1

From the periodic table you get the atomic masses of each element.

These are the values that I have in my periodic table (use those numbers of your periodic table if your teache gave you a specific one)

Na: 23 g/mol
O: 16 g/mol
H: 1 g/mol
C: 12 g/mol
Ca: 40 g/mol
S: 32 g/mol
Mg: 24 g/mol
P: 31 g/mol

Now I will do some examples and you do the others:

1) NaOH: 1 atom of Na * 23 g/mol + 1 atom of O * 16 g/mol + 1 atom of H * 1 g/mol

=> 1*23g/mol + 1*16g/mol + 1*1g/mol = 40 g/mol

2) H2O

=> 2 atoms of H * 1 g/mol + 1 atom of O * 16 g/mol = 2*1g/mol + 1*16g/mol = 18 g/mol

3) Glucose: C6H12O6

6*12 g/mol + 12 * 1g/mol + 6*16 g/mol = 72g/mol + 12g/mol + 96 g/mol = 180 g/mol

4) CaSO4:

1*40 g/mol + 1*32g/mol + 4*16g/mol = 136 g/mol

Now you only have to do the last one by your own.

Answer 2

40.00

18.02

180.18

136.15

262.87