Unit 1 Flashcards
list 4 factors that can speed up the rate of a reaction
- increasing concentration
- increasing surface area - decrease particle size
- increase temperature
- use a catalyst
formula for rate of reaction
Average rate = change in quantity/change in time
why does that average rate of a reaction decrease over time?
the reactants are being used up so the concentration of reactants are decreasing
what is a catalyst?
a substance that speeds up a chemical reaction but is not used up by the reaction
how are elements arranged in the periodic table?
in order of increasing atomic number
how are elements in the same group similar?
- they have the same number of outer electrons
- they have similar chemical properties
- they have the same valency
describe an atom
a nucleus containing protons and neutrons with electrons in orbit
what is the mass number of an atom?
the number of protons + neutrons
what is the atomic number of an atom?
the number of protons
how do you work out the number of neutrons in an atom?
mass number - the atomic number
what is the mass of an electron?
an amount so small its not worth working out
what is the charge of an electron?
-1
what is the mass of a proton?
1 atomic mass unit
what is the charge of a proton?
+1
what is the mass of a neutron?
1 atomic mass unit
what is the charge of a neutron?
0
what are isotopes?
atoms with the same atomic number but different mass number ( they have different numbers of neutrons)
what is the relative atomic mass of an element?
the average mass of an element
what is a covalent bond?
a shared pair of electrons holding non-metal atoms together
how are atoms in a covalent bond held together?
by the attraction between the positive nuclei and the shared pair of electrons
list the 7 diatomic elements
- nitrogen
- oxygen
- fluorine
- hydrogen
- iodine
- bromine
- chlorine
what does diatomic mean?
two atoms covalently bonded
what shape would a molecule with the formula XY have?
linear
what shape would a molecule with the formula XY^2 have?
angular
what shape would a molecule with the formula XY^3 have?
trigonal pyramidal
what shape would a molecule with the formula XY ^4 have?
tetrahedral
what is an ion?
an atom that has gained or lost electrons in charge ( they do this to be stable like the noble gasses)
ionic compounds are usually made from a metal and non-metal. which ion will be positively charged?
metal ion = positive
non-metal ion = negative
what is an ionic bond?
an electrostatic attraction between positive and negative ions
what structure do ionic compounds have?
crystal lattice
- each positive ion surrounded by a negative ion and each negative ion surrounded by positive ions
in general, do ionic substances have high or low melting and boiling points?
high
because strong bonds must be broken which requires a lot of energy
why do ionic substances only conduct electricity when heated until a liquid or in a solution?
because when they are liquid or are in a solution ions are free to move so the substance can conduct electricity
what happens at the electrodes when an ionic compound is electrolysed?
at the electrode the ion gains or loses electrons
the ion is drawn to the oppositely charges electrode
do ionic compounds usually dissolve in water?
yes
what type of bonding is present in substances that can conduct electricity without decomposing?
metallic
why can metals conduct electricity?
the electrons are delocalised so they are free to move
do covalently bonded substances usually conduct energy?
no
because there are no free charged particles free to move
what is the usual ending for a compound containing only 2 elements?
…ide
iron chloride
what does the compound ending in …ate or …ite mean?
oxygen is present
what is pH?
a measure of hydrogen ion concentration in a solution
what pH would a solution of equal concentrations of hydrogen and hydroxide ions have?
pH 7
what pH would a solution with a higher concentration of hydrogen ions than hydroxide ions have?
pH 1-6 (acid)
what pH would a solution with a higher concentration of hydroxide ions than hydrogen ions have?
pH 8-14 (alkaline)
why is water neutral? (pH 7)
when the molecules separate it makes equal concentrations of hydrogen and hydroxide ions
what pH will a solution of a soluble non-metal oxide be?
less than 7
what pH will a solution of soluble metal oxides be?
more than 7
what are bases?
a substance that can react with acids and neutralise them
what is an alkali?
a base that dissolves in water
what is a neutralisation reaction?
the reaction of an acid with a base that results in the pH moving towards 7.
complete the equation
metal oxide + water =
metal hydroxide
complete the equation
metal oxide + acid =
salt + water
complete the equation
metal hydroxide + acid =
salt + water
complete the equation
metal carbonate + acid =
salt + water + carbon dioxide
which salts are made from
- hydrochloric acid
- nitric acid
- sulphuric acid
- ethanoic acid
- chloride
- nitrate
- sulphate
- ethanoate
what effect on pH does adding water to an acid have?
increases it
what do you get when an acid reacts with a metal?
salt + hydrogen
what effect on pH does anything water to an alkili have?
decreases it
