How Do You Calculate Mass Percent of Compounds in a Mixed Sample?

[annayn]

A sample containing NaCl, Na2SO4, and NaNO3 gives the following elemental analysis: Na:32.8%; O: 36.01%; Cl:19.51%.
Calculate the mass percent of each compound in the sample

 

[Lyuokdea]

Try starting by calculating the mass percents for a pure sample of each of the three compounds.

~Lyuokdea

 

[Blueshift5]

Based on the given elemental analysis, the mass percent of each compound can be calculated as follows:

1. Mass percent of NaCl:
To calculate the mass percent of NaCl, we first need to determine the moles of Na and Cl present in the sample. Since the molar mass of NaCl is 58.44 g/mol, we can use the following equations:

Moles of Na = (32.8% / 100%) * (100g sample) / (22.99 g/mol) = 1.43 moles
Moles of Cl = (19.51% / 100%) * (100g sample) / (35.45 g/mol) = 0.55 moles

Now, we can use the molar ratio of NaCl (1:1) to determine the moles of NaCl present in the sample:
Moles of NaCl = 0.55 moles (since it is the limiting reactant)

Finally, we can calculate the mass of NaCl present in the sample:
Mass of NaCl = (0.55 moles) * (58.44 g/mol) = 32.17 g

Therefore, the mass percent of NaCl in the sample is:
Mass percent of NaCl = (32.17 g / 100 g sample) * 100% = 32.17%

2. Mass percent of Na2SO4:
To calculate the mass percent of Na2SO4, we first need to determine the moles of Na and S present in the sample. Since the molar mass of Na2SO4 is 142.04 g/mol, we can use the following equations:

Moles of Na = 1.43 moles (calculated in step 1)
Moles of S = (36.01% / 100%) * (100g sample) / (32.06 g/mol) = 1.12 moles

Now, we can use the molar ratio of Na2SO4 (2:1) to determine the moles of Na2SO4 present in the sample:
Moles of Na2SO4 = 1.12 moles (since it is the limiting reactant)

Finally, we can calculate the mass of Na2SO4 present in the sample:
Mass of Na2SO4 = (1.12 moles) * (142.04 g/mol) = 159.