Presentation on theme: "The Mole and Chemical Composition"— Presentation transcript:
1 The Mole and Chemical Composition Chapter 7The Mole and Chemical Composition
2 Avogadro’s Number Mole 6.022x10 23 /mole Can be: ions, molecules, atoms, formula units
3 Converting Amount of Moles to Number particles How many ions are there in0.187 mol of Na+ ions?0.187 mol Na+ (6.022*10^23 ions Na+/ 1 mol)= 1.13x10^23 ions Na+
4 How many formula units are there in 5.9 mol of NaOH? 5.9 mol NaOH (6.022x10^23 formula units/1 mol)= 3.55X10^24 formula units NaOH
5 O atoms in 3.161X1021 molecules of CO2 Determine the number of moles of each specified atom or ion in the give samples of the following compounds.O atoms in 3.161X1021molecules of CO2
6 Converting Number of Particles to Mass Given the molar mass of NaCl (58.44 g/mol), find the mass in grams of 3.34X 1023 formula units of NaCl
7 7.990x1025 molecules of CH4 (molar mass of CH4=16.05 g/mol) find the mass in grams.
8 Find the number of atoms in 237 g Cu (molar mass of Cu= 65.55 g/mol)
9 Average atomic massWeighted average of masses of all naturally occurring isotopes of an elementCalculate the average atomic mass ofoxygen. Its compositions is 96.4% ofatoms with a mass of amu,1.4% with a mass of17.00 amu,and 2.2% with a mass amu.
10 Chemical Formulas and mole composition Find the molar mass for the compound CaHPO4
11 Write the formula and then find the molar mass for calcium phosphate
12 Percent CompositionThe Percentage by mass of each element in a compound part/total x 100Find the percentage of bothelements in H2O
13 Find the % composition of a compound which contains 16. 56g C, 26 Find the % composition of a compound which contains 16.56g C, 26.22g F, and 4.14 g H
14 Empirical FormulaLowest whole number ratio of elements in a compound.
15 Steps for determining an Empirical Formula Percent to massMass to molesDivide each mole value by the smallest number of moles calculatedMultiply (or round) till whole
16 Example: A chemical analysis of a liquid shows that there is 60 Example: A chemical analysis of a liquid shows that there is 60.0% C, 13.4% H, and 26.6% O by mass. Calculate the empirical formula of the substance.
17 Molecular FormulaWhole-number multiples of empirical formulas.
18 Calculate the molecular formula of the compound whose molar mass is 60 Calculate the molecular formula of the compound whose molar mass is 60.0 g/mol and empirical formula is CH4N
19 Determine the molecular formula for a compound for a compound that has a molar mass of 34g and is 94.1% oxygen and 5.9% hydrogen.