Chemistry 101

Chapter 3: Calculations with Chemical Formulas And Equations

Calculate the formula weight of sodium chloride, NaCl.

What is the formula weight of glucose, C₆H₁₂O₆?

The total number of atoms in 0.10 mol of NO2 is?

How many moles of Na2SO4 are contained in a 35.0-g sample of this substance?

A 1.74 g sample of an element contains 7.887 x1021 atoms. What is the element symbol?

Which of the following substances contains the greatest mass of chlorine?

Calculate the number of moles of calcium in 2.53 moles of Ca3(PO4)2

How many g of iron are required to use up all of 25.6 g of oxygen atoms (O) to 
 form Fe2O3?

Calculate the mass percentages of the elements in formaldehyde (CH2O) molar 
 mass = 30g/mol

Calculate the empirical formula of a compound whose percentage composition 
 data is 43.64% P and 56.36% O. If the molar mass is determined to be 283.9 g/mol, 
 what is the molecular formula?

The combustion of a 13.660 g sample of a compound of C, H, and S in pure oxygen 
 gave 19.352 g CO2 and 11.882 g of H2O. Calculate the empirical formula of the 
 compound.

An organic compound contains by mass. Its composition is 68.85% C, 4.95% H, and 
 26.2% O, and its molecular weight is 122.12 g/mol. What is its molecular formula?

What are the masses of CO2 and H2O produced by the combustion of 1.397 g of a 
compound with empirical formula C3H6O2 (molar mass = 74.079 g/mol)

A compound contains only carbon, hydrogen and oxygen. The compound is 48.0% 
 C and 4.04% H by mass, and its molar mass is 100. g/mol. What is the molecular 
 formula of the compound? 
 (Molar masses (g/mol) are: C = 12.01: H = 1.01 and O = 16.00)

If 2.89 g of an osmium oxide contains 2.16 g of osmium (molar mass = 190.23 
 g/mol). What is the empirical formula of the oxide?

When 6.40 g of CH3OH was mixed with 10.2 g of O2 and ignited, 6.12 g of CO2 was 
 obtained. What was the percentage yield of CO2? 
 2CH3OH + 3O2 -&gt; 2CO2 + 4H2O 
 MM(g/mol) (32.04) (32.00) (44.01) (18.02)

If 6.91 grams of ZnO are obtained from a reaction of 6.54 g Zn with excess of 
 oxygen. What is the percent yield of the reaction? 
 (Molar mass: Zn = 65.38 g/mol; O= 16.00 g/mol)

Considering the chemical equation below 
 4KO2(s) + 2H2O(l) → 4KOH(s) + 3O2(g) 
 When 4.50 g of KO2 was reacted, the percent yield of oxygen was 73.2 %. What was 
 the actual yield of oxygen?

A 2.30 g sample of CaO (56.1 g/mol) is reacted with excess water and 2.14 g of 
 Ca(OH)2 (74.1 g/mol) is produced. What is the percent yield of the reaction? 
 CaO(s) + H2O (l) → Ca(OH)2(s)

If 2.00 moles of SiO2 and 4.00 moles of C reacted according to the equation below, 
 calculate the theoretical yield of CO produced (molar mass of CO = 28.0 g/mol). 
 SiO2 +3C → SiC + 2CO