Relative Atomic Mass
Potassium has an atomic mass of 39.1 u. What does this mean?
A potassium atom weighs 39.1 times as much as a hydrogen atom
What is the definition of a mole?
a quantity equal to the number of atoms in the atomic mass of any element expressed in grams
How do you related the quantity of a substance to another quantity of the same substance?
Through the Mole
Empirical vs Molecular formula
What are the differences?
Empirical = the simplest integral ratio of the different types of atoms in the compound
Molecular= the actual number of each type of atom in each molecule of the compound
0.72 L of 2.5 M NaOH = _________ mol NaOH
1.8 mol NaOH
Calculate the Molar Mass of CaCO3
100.087 g/mol
What does a mole of gold weigh?
196.97 g
What is the mass in grams of a chlorine atom?
5.90 x10-23 g Cl
Trinitrotoluene (C7H5O6N3) is an explosive commonly referred to as TNT. Calculate the percentage of nitrogen by mass in this compound.
7 C (7 × 12.0 g)/mol = 84.0 g/mol
5 H (5 × 1.0 g)/mol = 5.0 g/mol
6 O (6 × 16.0 g)/mol = 96.0 g/mol
3 N (3 × 14.0 g)/mol = 42.0 g/mol = 18.5%
MM= 227 g/mol
How many Na+ ions are dissolved in 1.5 L of 3.0 M Na2CO3?
5.4 × 1024 ions Na +
Calculate the Molar mass of (NH4)2SO4
132.17 g/mol
What is the mass of 0.32 mol of sodium nitrite?
22 g NaNO2
How many molecules are in 1.000 mg of the organic solvent, carbon tetrachloride?
3.91x1018 molecules CCl4
Many salts are hydrated, which means they have water molecules incorporated into their ionic crystal lattice in a fixed ratio. Magnesium sulfate heptahydrate, MgSO4 ∙ 7 H2O, has seven water molecules incorporated into the crystal lattice for each magnesium ion and sulfate ion. Calculate the percentage of water by mass in MgSO4 ∙ 7 H2O.
1 Mg (1 × 24.3 g)/mol = 24.3 g/mol
1 S (1 × 32.0 g)/mol = 32.1 g/mol
4 O (4 × 16.0 g)/mol = 64.0 g/mol 120.4 g/mol
7 H2O (7 × 18.0 g)/mol = 126.0 g/mol = 51.1%
MM= 246.4 g/mol
The fluid inside living cells is called cytosol. A human hepatocyte (a type of liver cell) with a volume of 500 fL (1 fL (femtoliter) = 10−15 L) contains 12 mM Na+. How many sodium ions are in the cytosol of this cell?
3.6 × 109 ions Na+
A 10.000 g sample of zubenium fluoride (ZuF) is decomposed and 8.503 g of Zu is recovered.
What is the atomic mass of zubenium?
108 u
Carbon dioxide, produced by respiration in plants and animals, causes the slightly acidic nature of normal rain. How many molecules of CO2 are in 0.725 mol CO2?
4.36x1023 molecules CO2
Dinitrogen tetroxide (N2O4) is one of the most important rocket propellants ever developed. How many oxygen atoms are in 27.2 L of the gas at STP?
2.92 x 1024 atoms O
A sample of caffeine is analyzed and found to contain 1.4844 g C, 0.1545 g H, 0.4947 g O and 0.8661 g N. Determine the empirical formula of caffeine.
C4H5ON2
As a glass of cold tap water warms up, small air bubbles will come out of solution on the inner wall of the glass. A glass of cold water contains 0.45 mM O2. How many milliliters of oxygen gas at STP are dissolved in 300.0 mL of this water?
3.0 mL O2
A compound of copper and oxygen contains 13.073 g Cu and 1.647 g O. Oxygen has an atomic mass of 16.0 u.
What is the atomic mass of copper if the formula of the above compound is CuO?
127 u
Bluestone is an attractive mineral with the chemical name copper(II) sulfate pentahydrate. What is the mass of a 1.75 mol sample of bluestone?
437 g CuSO4 * 5H2O
Mercury is a liquid metal with a density of 13.546 g/mL at 20°C. How many Mercury molecules are in 25 mL of Mercury?
1.688 mol = 1.7 mol
A sample of ascorbic acid, also known as vitamin C, was analyzed and found to contain 1.080 g C, 0.121 g H, and 1.439 g O. Ascorbic acid has a molar mass of 176.1 g/mol. Determine the molecular formula of ascorbic acid.
C6H8O6
In a solution of Fe2(SO4)3:
if the [SO4 2−] = 3.0 M then what is the [Fe3+]?
2.0 M Fe3+