Homework: Read Pages Do all of % composition worksheet Mole problems 3 Packet Next Quiz: Monday Feb 25 or Tues Feb 26 Test: March 11 th (Monday) or March 12 th (Tuesday)

Percent Composition Lesson 3 Determining the formula of a compound % by mass of each element in a compound

% Composition If 8.20 grams of magnesium combines with 5.40 grams of oxygen to form a compound, what is the % composition of this compound?

% composition 9.03 grams of Mg combine completely with 3.48 grams of nitrogen

% Composition of a known compound

% composition of C 3 H 8

% composition of each element in sodium bisulfate

Homework Read: pages Worksheet: Finding Empirical and Molecular Formulas More Mole problems WS II # 1-6 Test: March 11 th and 12 th

Mole Problems Liters moles grams Liters g/L

Mole Problems grams grams grams *10 23 atoms grams

Mole Problems *10 22 molecules NaOH grams L 4.3* grams

1. HCN 3. Ca(NO 3 ) % H 24.42% Ca 44.43% C 17.07% N 51.83% N 58.50% O 2. H 2 O 4. Al 2 (CO 3 ) % H 23.06% Al 88.79% O 15.40% C 61.54% O Percent Composition

More Mole Problems Question 1Question x g 2.11 x atoms Question 2Question moles area = cm 3 = mL Question x atoms moles1.02x10 24 atoms Question 4 a)2.1 x molecules b)183 g

More Mole Problems Question 7 a)5.1 mol b)1.86 x atoms c)182 mL Question x10 16 molecules Question 9

Finding Empirical and Molecular Formulas Question 1Question 4 a)C 3 H 4 O 3 CH 2 Cl C 2 H 4 Cl 2 b)CH 2 OQuestion 5 c)CH 2 OC 4 H 5 N 2 O Question 2 CH 5 N empirical CH 5 N molecular Question 3 Question 6 P 2 O 5 SN empirical; S 4 N 4 molecular

More Mole Problems Worksheet No.3 Answers 2) STP: 0°C, 1 atm (760 mmHg, kPa) 3) 1.96 g/L 4) 6.19 x molecules 5) 20 moles 6) 19.97% 7.a) 5.78 x10 22 atoms 7.b) g 7.c) air: 1.25 g/L; bag: g/L,  bag will not float 8) 4.70% 9) 5 glasses

Empirical Formula Lowest whole number ratio of atoms of the elements in a compound.

Calculate the empirical formula of a compound that is 25.9% nitrogen and 74.1% oxygen Step 1: find mole ratio Step 2: divide by least # of moles Step 3: multiply to get a whole number

Molecular Formulas Molecular formulas are whole number multiples of the empirical formulas The empirical formula and the MM of the molecular formula is needed!

What is the empirical formula of a compound that is 27.3% C and 72.7% O?

Calculate the molecular formula given the empirical formula is CO 2 and has a molar mass of grams/mol 1.Find the MM of the empirical formula 2.Divide the MM of the molecular formula by the MM of the empirical formula 3.Multiply all elements by the whole # to get the molecular formula