quantitative chemistry sl. si units modern science is an international endeavour, more reliable...
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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 – m3
• 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 (Ar)
• 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: H2
Relative Molecular Mass (Mr)
• Relative molecular mass is calculated by adding the relative atomic masses of the atoms making up the molecule– Ex: H2O - 18.01g
Relative Formula Mass (Mr)
• 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 carbon12, 12C = 12g
• L= 12.01g/ 1.99265x10-23g= 6.02x1023
– 1.99265x10-23 is mass of one carbon atom– 12.01g is mass of one mole of carbon12
• 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: H2O2 = HO
– Ex: C6H12O6 = CH2O
Molecular Formula
• Molecular Formula is the actual amount of elements present– Ex: Glucose• Molecular Formula = C6H12O6
• Empirical Formula = CH2O
Finding Hydrocarbon
• Hydrocarbon is any compound contain only hydrogen and carbon in its structure
• Empirical formula is CH2
• Molecular formula is CnH2n
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: 2H2 + O2 2H2O
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__CH4 + __O2 __CO2 + __H2O
1 CH4 + __O2 1 CO2 + __H2O
1 CH4 + __O2 1 CO2 + 2 H2O
1 CH4 + 2 O2 1 CO2 + 2 H2O
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
• 2C2H2 + 5O2 4CO2 + 2H2O2mol 4moln(CO2) = 4 = 2:1 mole to mole ratio
n(C2H2) 2
M(C2H2) = (2x12.01) + (2x1.01) = 26.04g/mol
m(C2H2) = 1 mol = 0.0384g
26.04g/mol
Continue…M(CO2) = (12.01) + (2x15.99) = 44.00g/mol
m(CO2) = 1 mol = 0.0227g x 2 =0.0455g
44.00g/mol
Continue…1g C2H2 ? CO2
mtotal(CO2) = (44.01g/mol)x(2mol)x(1.00g)
(26.04g/mol)x(1mol)= 3.38g
Material Covered
• HL Book pages 1 - 13
Study Questions
• Ex: 1 – 13• PQ: 1 – 4 • Quiz: 1 #1-29