Percent composition and molecular formula (practice)

Calculate the formula for the following hydrate composed of 76.9% CaSO3 and 23.1% H2O. CaSO3 • H2O CaSO3 • 2H2O CaSO3 • 3H2O What is the molar mass of the anhydrous compound? Answer using four significant figures. 36.02 g/mol 120.15 g/mol 156.12 g/mol

CaSO3: 2H2O 120.15 g/mol

Identify the correct mole ratio for each substance. Sodium chloride (NaCl)-Na:Cl = 1: Ammonium nitrate (NH4NO3)-H:O = 4: Calcium bicarbonate (Ca(HCO3)2)-Ca:H:C:O = 1:2:2 Lithium sulfide (Li2S)-Li:S = 2:

1 3 6 1

A 50.51g sample of a compound made from phosphorus and chlorine is decomposed. Analysis of the products showed that 11.39 g of phosphorus atoms were produced. Answer using three significant figures. What is the percent by mass of phosphorus? What is the percent by mass of chlorine?

22.5% 77.5%

Carbon dioxide (CO2) is a gaseous compound. Calculate the percent composition of this compound. Answer using three significant figures. What is the percent by mass of carbon? What is the percent by mass of oxygen?

27.3% 72.7%

What is the percent by mass of sodium (Na) in sodium chloride? 39.3% 22.9% 0.393%

39.3%

Table salt is the compound sodium chloride (NaCl). Use the periodic table to find the molar mass of NaCl.

58.44

What is the percent by mass of chlorine (Cl) in sodium chloride? 35.5% 60.7% 0.606%

60.7%

What is the percentage of water in the following compound? Answer using three significant figures. Sodium carbonate decahydrate, Na2CO3 • 10H2O % by mass H2O

63.0%

The empirical formula for a compound is CH2. Its molar mass is 140.1 g/mol. What is its molecular formula? CH2 C10H20 C5H10 C20H10

C10H20

The empirical formula of an artificial sweetener is C14H18N2O5. The molecular mass of the sweetener is 294.34 g/mol. What is the molecular formula of the artificial sweetener? C7H9NO2 C7H9NO3 C14H18N2O5 C28H36N4O10

C14H18N2O5

Molecular formula: C6H12O6 Empirical formula: C6H12O6 C2H4O2 CH2O CHO

CH2O

A compound is 42% sodium, 19% phosphorus, and 39% oxygen by mass. What is the empirical formula of this compound? Na3PO4 NaPO Na9P4O8 Na4P3O

Na3PO4

A sample of a compound contains 9.11 g Ni and 5.89 g F. What is the empirical formula of this compound? NiF Ni3F2 NiF2

NiF2

If the molar mass of the compound is 96.69 g/mol, what is the molecular formula of the compound? NiF2 NiF Ni2F4

NiF2

A compound is found to contain 50.05% sulfur and 49.95% oxygen by mass. What is the empirical formula for this compound? SO S2O SO2 What is the empirical mass of that compound? Answer using four significant figures.

SO2 64.07g

NaHCO3 empirical molecular both

both