The Mole

Atoms & molecules are extremely small The number of individual particles in even a small sample of something is very large Therefore, counting the number of particles is not a practical way to measure the sample. The Mole

A chemical counting unit (abbreviated “mol”) Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000, X (in scientific notation) The Mole

6.02 x Amedeo AvogadroThis number is named in honor of Amedeo Avogadro, who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present in a constant volume of gas. The Mole That’s my number!

The term representative particle refers to the species present in a substance –Usually atoms or molecules The Mole

Molar Relationships A balanced chemical equation can be interpreted in numbers of molecules, but generally chemists interpret equations as “mole-to-mole” relationships. 2H 2 (g) + O 2 (g) → 2H 2 O (l) In the equation above: 2 moles of hydrogen gas and 1 mole of oxygen gas produce 2 moles of liquid water.

Molar Relationships Therefore: H 2 & O 2 have a 2:1 mole-to-mole ratio O 2 & H 2 O have a 1:2 mole-to-mole ratio H 2 & H 2 O have a 1:1 mole-to-mole ratio 2H 2 (g) + O 2 (g) → 2H 2 O (l)

Molar Relationships What are the mole-to-mole ratios in the chemical equation above? N 2 + 3H 2 → 2NH 3

Find the number of moles of NH 3 that can be formed from 4.8 mol H 2 using the balanced reaction below. N 2 + 3H 2 → 2NH 3 Molar Relationships 4.8 mol H 2 2 mol NH 3 3 mol H 2 x = 3.2 mol NH 3

Find the number of moles of LiNO 3 needed to produce 3.2 mol Pb(NO 3 ) 4 using the balanced reaction below. Pb(SO 4 ) 2 + 4LiNO 3  Pb(NO 3 ) 4 + 2Li 2 SO 4 Molar Relationships 3.2 mol Pb(NO 3 ) 4 4 mol LiNO 3 1 mol Pb(NO 3 ) 4 x = 12.8 mol LiNO 3

Practice Problems Grab your clicker! (& a calculator)

Consider the balanced chemical reaction: 2Fe + 3 H 2 S0 4 → Fe 2 (SO 4 ) 3 + 3H 2 How many moles of Fe are required to produce 9 moles of H 2 ? A. 9 moles B. 2 moles C. 4.5 moles D. 6 moles Question #1

Consider the balanced chemical reaction: 2Fe + 3 H 2 S0 4 → Fe 2 (SO 4 ) 3 + 3H 2 How many moles of Fe 2 (SO 4 ) 3 will be produced if we begin with 17 moles of Fe? A. 17 moles B. 8.5 moles C. 34 moles D. 11 moles Question #2

Consider the balanced chemical reaction: 2C 2 H 6 + 7O 2 → 6H 2 O + 4CO 2 How many moles of carbon dioxide are produced from 1 mole of C 2 H 6 ? A. 1 moles B. 2 moles C. 7 moles D. 8 moles Question #3

Consider the balanced chemical reaction: 2C 2 H 6 + 7O 2 → 6H 2 O + 4CO 2 How many moles of O 2 are required to produce 9 moles of H 2 O? A moles B. 6 moles C. 9 moles D. 7.5 moles Question #4

Consider the following chemical reaction: KOH + H 3 PO 4 → K 3 PO 4 + H 2 O How many moles of KOH are required to produce 12.5 moles of H 2 O? A. 2.5 moles B. 7.5 moles C. 9 moles D moles Question #5

Consider the following chemical reaction: KOH + H 3 PO 4 → K 3 PO 4 + H 2 O How many moles of H 3 PO 4 are required to produce 9 moles of H 2 O? A. 3 moles B. 6 moles C. 9 moles D. 7 moles Question #6