Quantitative Chemistry SL

SI Units Modern science is an international endeavour, more reliable system of standards of measure, the System International Units aka SI Units

SI Units What’s measurement – how it is measurement - symbol Mass – kilogram – kg Time – second – s Temperature – kelvin – K Volume – cubic metre – m 3 Pressure – pascal - Pa

Substance Atom – the basic unit of matter Element – identifier of an atom Compound – combination of two or more atoms Molecule – amount of atoms present for one or more elements Ions – amount of atoms present for one element

Mole A mole is the amount of a substance which contains the same number of chemical species as there are atoms in exactly 12 grams of the isotope carbon-12. Symbol – mol – Ex: 1 mole of Hydrogen means one Hydrogen atom is present

Relative Atomic Mass (A r ) Relative atomic mass is the mass of one mole of atoms of an element – Ex: one mole of hydrogen has a mass of 1.01g

Molecular Formula Composition of elements symbols to represent a molecule – Ex: H 2

Relative Molecular Mass (M r ) Relative molecular mass is calculated by adding the relative atomic masses of the atoms making up the molecule – Ex: H 2 O g

Relative Formula Mass (M r ) Relative formula mass is calculated by adding the relative atomic masses of the atoms making up the ionic compound – Ex: NaCl = 58.33g

Avogadro’s Number (L) Avogadro’s number is the number of atoms in one mole of carbon 12, 12 C = 12g L= 12.01g/ x g= 6.02x10 23 – x is mass of one carbon atom – 12.01g is mass of one mole of carbon 12 We use this number for number of atoms in one mole of an element and the number of molecules

Empirical Formula Empirical Formula is the simplest ratio of the elements in a chemical compound – Ex: H 2 O 2 = HO – Ex: C 6 H 12 O 6 = CH 2 O

Molecular Formula Molecular Formula is the actual amount of elements present – Ex: Glucose Molecular Formula = C 6 H 12 O 6 Empirical Formula = CH 2 O

Finding Hydrocarbon Hydrocarbon is any compound contain only hydrogen and carbon in its structure Empirical formula is CH 2 Molecular formula is C n H 2n

Chemical Equation Chemical equation is a representation of a chemical reaction using symbols Reactants are the elements that will under go a chemical reaction Products are the elements that under went a chemical reaction All reactants must be present in the products to satisfy the law of conservation of matter – Ex: 2H 2 + O 2 2H 2 O

Balancing Equations Start with the element there is the least number of present Finish with the element that has the most present

Balancing Equations Example __CH 4 + __O 2 __CO 2 + __H 2 O 1 CH 4 + __O 2 1 CO 2 + __H 2 O 1 CH 4 + __O 2 1 CO H 2 O 1 CH O 2 1 CO H 2 O

Mass and gaseous volume relationships in chemical reactions Write the equation for the reaction Write the amounts in moles of the relevant reactants and products of interest from the equation and show the relationship between them Convert the known data given into moles to find moles of the substance required Convert the number of moles to required quantities(mass, volume, etc…)

Mass and gaseous volume relationships in chemical reactions 2C 2 H 2 + 5O 2 4CO 2 + 2H 2 O 2mol 4mol n(CO 2 ) = 4 = 2:1 mole to mole ratio n(C 2 H 2 ) 2 M(C 2 H 2 ) = (2x12.01) + (2x1.01) = 26.04g/mol m(C 2 H 2 ) = 1 mol = g 26.04g/mol

Continue… M(CO 2 ) = (12.01) + (2x15.99) = 44.00g/mol m(CO 2 ) = 1 mol=0.0227g x 2 =0.0455g 44.00g/mol

Continue… 1g C 2 H 2 ? CO 2 m total (CO 2 ) = (44.01g/mol)x(2mol)x(1.00g) (26.04g/mol)x(1mol) = 3.38g

Material Covered HL Book pages

Study Questions Ex: 1 – 13 PQ: 1 – 4 Quiz: 1 #1-29