Ch.2 - Atoms & ElementsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Sections
The Atom
Subatomic Particles
Isotopes
Ions
Atomic Mass
Periodic Table: Classifications
Periodic Table: Group Names
Periodic Table: Representative Elements & Transition Metals
Periodic Table: Element Symbols
Periodic Table: Elemental Forms
Periodic Table: Phases
Periodic Table: Charges
Calculating Molar Mass
Mole Concept
Law of Conservation of Mass
Law of Definite Proportions
Atomic Theory
Law of Multiple Proportions
Millikan Oil Drop Experiment
Rutherford Gold Foil Experiment
Additional Practice
Thomson's Cathode Ray Tube Experiment
The Chadwick Neutron Experiment
Mass Spectrometry
Additional Guides
Periodic table Charges (ignore)
Calculating Molar Mass (ignore)
Calculating Grams to Moles
LearnAdditional Practice
Next SectionMole Concept

Molar Mass is a physical property that represents the mass of a substance divided by the amount of that substance.

Calculating Molar Mass

Concept #1: Calculating Molar Mass

The units for molar mass are in grams per mole. 

Example #1: Calculate the molar mass of the compound (NH4)2SO4.

Practice: Calculate the molecular weight of C3H5N3O3.

Practice: The reaction between nickel metal and hydrochloric acid is not a simple dissolution. The product formed is NiCl2 • 6 H2O (s), nickel (II) chloride hexahydrate, which has exactly 6 waters of hydration in the crystal lattice for every nickel ion. What is the molar mass of nickel (II) chloride hexahydrate, NiCl2 • 6 H2O (s)?

Practice: What is the molar mass of diazepam also known as Valium if 0.05570 mol weighs 15.86 g?

Previous SectionPeriodic Table: Charges
Next SectionMole Concept
Additional Problems
A single atom of a certain element has a mass of 3.352 x 10 -23 g. The element is a. Ne b. Co c. Al d. Br e. Ti
What is the molar mass of calcium phosphate, Ca 3(PO4)2? a. 87.05 g/mol b. 215.21 g/mol c. 278.18 g/mol d. 279.21 g/mol e. 310.18 g/mol
One molecule of a compound weighs 2.03 x 10 -22 grams. Calculate the molar mass of this molecule. a. 3.37 x 10-46 g/mol b. 3.36 x 10-23 g/mol c. 1.23 x 10-21 g/mol d. 1.22 x 10 2 g/mol e. 1.21 x 1024 g/mol
A compound has a formula of Y2O5. If 2.8 g of Y combines with 8.0 g of oxygen, what is the atomic weight of Y? A. 10 B. 12 C. 14 D. 16 E. 18
What is A, if 64.0 g of A combines exactly with 142 g of Cl to give the compound ACl 2? A. Br B. Mg C. Ca D. S E. Ba
What is the atomic weight of an element, X, if 1.00g of X combines with 0.66 g of oxygen to form a compound XO3? A. 24 B. 67 C. 73 D. 100 E. 146
If the mass of 2.51 x 10 -3 moles of compound A is 0.452 g, then what is the molar mass?
A sample of a compound of xenon and fluorine contains molecules of a single type; XeFn , where n is a whole number. If 9.03 x 10 20 of these XeFn molecules have a mass of 0.311 g, what is the value of n? a) 2 b) 3 c) 4 d) 6
A 3.41 x 10–6 g sample of a compound is known to contain 4.67 x 10 16 molecules. This compound is a) CO2 b) CH4 c) NH3 d) H2O
A single molecule of a certain compound has a mass of 3.4 x 10 –22 g. Which value comes closest to the mass of a mole of this compound? a) 50 g•mol–1 b) 100 g•mol–1 c) 150 g•mol–1 d) 200 g•mol–1
A 2.000 g sample of an unknown metal, M, was completely burned in excess O 2 to yield 0.02224 mol of the metal oxide, M2O3. What is the metal? A. Y B. Ca C. Al D. Sc
If 2.50 grams of an unknown compound contains 6.25 x 10 19 molecules, what is its molecular mass?   
What is the molar mass of aspartic acid, C 4O4H7N?  A) 43.03 g/mol B) 70.02 g/mol C) 86.91 g/mol D) 133.11 g/mol      E) 197.98 g/mol
A 20.0 g sample of an element contains 4.95 x 1023 atoms. Identify the element. A) Cr B) O C) Mg D) Fe
If 4.05 x 1023 molecules of a substance have a mass of 86.2 g, what is the molar mass of the substance? A)  128 g/mol B)  3.49 x 1025 g/mol                                    C)  2.13 x 1022 g/mol D)  4.70 x 1021 g/mol           E)  58.0 g/mol
Calculate the molar mass for Mg(ClO4)2. A) 247.52 g/mol B) 119.52 g/mol C) 123.76 g/mol D) 223.21 g/mol E) 75.76 g/mol
What is the molar mass of calcium permanganate? A) 199 g/mol B) 278 g/mol C) 216 g/mol D) 159 g/mol
What is the identity of substance X if 0.380 mol of X weighs 17.5 g? A) NO2 B) N2O C) N2O4 D) NO3
Calculate the molar mass for Mg(ClO4)2. A) 223.21 g/mol B) 123.76 g/mol C) 119.52 g/mol D) 247.52 g/mol E) 75.76 g/mol
6.02 x 10 21 molecules of an unknown substance X has a mass of 2.00 grams. What is the molar mass of X in g/mole? (A) 0.02 g/mol (B) 0.2 g/mol (C) 20 g/mol (D) 200 g/mol (E) 2000 g/mol
Calcium fluoride is used to fluoridate drinking water. Calculate its molar mass in g/mol. (A) 118.15 (B) 99.15 (C) 78.07 (D) 59.08 (E) 38.00
6.02 x 1021 molecules of an unknown substance X has a mass of 11.0 grams. What is the molar mass of X in g/mole? (A) 110 g/mol (B) 220 g/mol (C) 1100 g/mol (D) 2200 g/mol (E) cannot be determined without the formula of X
If 2.50 grams of an unknown compound contains 6.25 x 1019 molecules, what is its molecular mass? 
How many grams of P is contained in one mole of Mg 3(PO4)2?   
A 67.2 g sample of a gold and palladium alloy contains 2.49 x 10 23 atoms. What is the composition (by mass) of the alloy? 
A 7.36-g sample of copper is contaminated with an additional 0.51 g of zinc. Suppose an atomic mass measurement was performed on this sample. What would be the measured atomic mass?
Calculate the formula mass for each compound. a. MgBr2
Calculate the formula mass for each compound. b. HNO2
Calculate the formula mass for each compound. c. CBr4
Calculate the formula mass for each compound. d. Ca(NO3)2
The Freons are a class of compounds containing carbon, chlorine, and fluorine. While they have many valuable uses, they have been shown to be responsible for depletion of the ozone in the upper atmosphere. In 1991, two replacement compounds for Freons went into production: HFC-134a (CH2FCF3) and HCFC-124 (CHClFCF3). Calculate the molar masses of these two compounds.
Calculate the molar mass of the following substances.
Calculate the molar mass of the following substances.b. Ca 3(PO4)2
Calculate the molar mass of the following substances.c. Na 2HPO4
Bauxite, the principal ore used in the production of aluminum, has a molecular formula of Al2O3 • 2H2O.a. What is the molar mass of bauxite?
Bauxite, the principal ore used in the production of aluminum, has a molecular formula of Al2O3 • 2H2O. The • H2O in the formula are called waters of hydration. Each formula unit of the compound contains two water molecules.a. What is the molar mass of bauxite?
The molecular formula of acetylsalicylic acid (aspirin), one of the most commonly used pain relievers, is C9H8O4. a. Calculate the molar mass of aspirin.
Chloral hydrate (C2H3Cl3O2) is a drug formerly used as a sedative and hypnotic. It is the compound used to make “Mickey Finns” in detective stories.a. Calculate the molar mass of chloral hydrate.
Dimethylnitrosamine, (CH3)2N2O, is a carcinogenic (cancer-causing) substance that may be formed in foods, beverages, or gastric juices from the reaction of nitrite ion (used as a food preservative) with other substances.a. What is the molar mass of dimethylnitrosamine?
Calculate the molar mass of Ca 3(PO4)2.A) 215.21 g/molB) 246.18 g/molC) 279.21 g/molD) 87.05 g/molE) 310.18 g/mol
What is the molar mass of aspartic acid, C4O4­H7N?A) 43.03 g/mol     B) 70.56  g/mol                C) 133.11 g/mol               D) 197.11 g/molE) 206.33 g/mol
What is the molecular weight of glucose, C6H12O6
One molecule of a compound weighs 2.03 x l0 - 22 g. The compound is:a) SOb)SiO4 c)Al2O3 d)PdOe) none of these   
An ionic compound has the formula MCl2. The mass of 0.3011 mol of the compound is 62.69 grams. What is the identity of the metal? a. Ni b. Cu c. Ba d. Hg e. Sn  
An atom of an element weights 9.12 x 10-23 g. What is the atomic mass of this element in atomic mass units?a. 45.0 b. 54.9c. 55.8d. 58.7e. 63.5
How many atomic mass units is 1 mole of water? 
What is molar mass of Na 2CO3?
Calculate the molar mass of sodium chloride, NaCl (from the periodic table Na = 22.99 and Cl = 35.45).a) 6.745 g/moleb) 58.44 g/molec) 74.55 g/moled) 67.45 g/molee) 19.00 g/mole
Calculate the molar mass of Cl 2 if 1.27 x 1022 molecules of gaseous Cl 2 have a mass of 1.5g.
What is the molar mass of calcium phosphate, Ca 3(PO4)2?
Determine the molar mass of sodium bicarbonate (from periodic table).molar mass of Na _____ x 1 mol Na = _____molar mass of H _____ x 1 mol H = _____molar mass of C _____ x 1 mol C = _____molar mass of O _____ x 3 mol O =Sum for total molar mass _____
Rank from highest to lowest molecular mass:D216O17O                 T 218O2                               D216O2  D218O2                         T216O2                                  H217O2T217O2                          H216O17O                     H  218O2
Glucose is the type of sugar the human body metabolizes to produce energy. Calculate the formula mass of glucose, C6H12O6.a. 220.02 amub. 340.00 amuc. 180.18 amu
The molecular mass of sodium oxide (Na 2O) is a. 61.97894b. 45.97954c. 22.98977d. 38.98917
Calculate the molar mass of each of the following compounds:(d) silver sulfate, Ag2SO4 
Calculate the molar mass of ALUM, KAl(SO 4) 2 . 12H2O or potassium aluminum sulfate dodecahydrate. Be sure to include the twelve waters of hydration in the molar mass.
Which definition best describes the term molar mass? (a) the mass, in ounces, of one mole of a substance (b) the mass, in grams, of one mole of a substance (c) the mass of one gram of a substance (d) the mass in units of moles
What is the molar mass of aspirin, C9H8O4?
What is the mass (g) of exactly 1 mol of the following compounds? N2O5Fe(ClO)2Fe(ClO3)3
Determine the molar mass of potassium hydrogen phthalate (KHP). The molecular formula is KHC8H4O4 .
The 69.5-g sample of the compound X3O4 contains 19.2 g of oxygen atoms. What is the molar mass of element X?
An unknown compound has the following chemical formula: N2Ox where x stands for a whole number. Measurements also show that a certain sample of the unknown compound contains 3.7 mol of oxygen and 2.45 mol of nitrogen. Write the complete chemical formula for the unknown compound.
Calculate the molar mass of each compound given below. Keep at least one decimal place in atomic masses from the periodic table.a. LiCl ________ g/molb. K3N__________ g/mol 
What is the molar mass of magnesium hydroxide, Mg(OH) 2, a common antacid?(A) 58 g/mol(B) 56 g/mol(C) 42 g/mol(D) 41 g/mol
Calculate the molar mass of potassium hydroxide (KOH).
Calculate the molar mass of ammonium phosphate (NH 4)3PO4 to correct sig. fig.