IB Chemistry Topic 1-Quantitative Chemistry

atom

the smallest unit of an element

molecules

atoms joined together to form the smallest particles

diatomic

when an element only appears on its own if it is bonded to itself

compounds

made up of more than one element, chemically bonded together

mole

6.02 x 10^23 is the number of atoms in an elements molar mass

isotope

atoms of an element with the same number of protons but different number of neutrons and thus a different mass

relative atomic mass

weighted mean mass of all the naturally occurring isotopes of an element

elements

the simplest forms of matter, cannot be broken down chemically into anything simpler

proton

sub atomic particle inside the nucleus with a positive charge and a relative atomic weight of 1

neutron

sub atomic particle inside the nucleus with a neutral charge and a relative atomic weight of 1

Avogadro's constant (number)

6.02 x 10^23

relative molecular mass

relative atomic mass for molecules

molar mass

the mass of a molecule in grams per mole

empirical formula

the simplest whole number ratio of atoms of each element in a particle of the substance

Calculating empirical formulas

1. Add oxygen mass and assume there is 100g of the compound

2. Divide the mass of each element by its atomic mass

3. Find the simplest whole number ratio

Molecular formula

the actual number of atoms of each element in a molecule of a substance

Calculating molecular formula

1. Find empirical formula

2. Add the relative atomic masses of all the elements multiplied by their respective number from the empirical formula

3. Divide the relative molecular mass by that number

4. Multiply each empirical formula number by this new number

Structural formula

shows the arrangement of atoms and bonds within a molecule

Cl Cl

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Cl - C - C - H

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H H

Isomers / Structural isomers

two compounds with the same molecular formula but different structural formulas. Basically same atoms with same amounts but bonded differently

Properties of chemical reactions

new substances formed, bonds are broken and reformed resulting in energy change between reacting system and surroundings, There is a fixed relationship between the number of particles of reactants and products and no overall change in mass

Stoichiometrically balanced

An equation with the correct coefficients (number of moles) in front of all of the compounds

state symbols

symbols placed after compounds in equations to denote their form

(s)=solid

(l)=liquid

(g)=gas

(aq)=in an aqueous solution

spectator ions

ions that remain in a solution undergoing a chemical reaction but do not change themselves

quantity measurement of solids

measure mass in kilograms

quantity measurement of liquids

measure density in (g cm⁻³) or (kg dm⁻³)

quantity measurement of aqueous solutions

measure concentration in (mol dm⁻³)

quantity measurement of gas

measure in mass or volume (pV=nRT)

solution

the mixture of both a solvent and a solute

solvent

what the solute is dissolved into

solute

is dissolved into a solvent

Avogadro's law

equal volumes of different gases at the same temperature and pressure have the same number of particles

limiting reagent

when one of the reactants is in excess and thus some will be left over unreacted

yield

the amount of product that s actually obtained experimentally

percentage yield

actual yield divided by percentage yield