UNIT 1 Flashcards
What are the four indicators of a chemical reaction?
Colour change, effervescence, precipitation, temperature change
What is a reactant?
a substance that is involved in a chemical reaction and becomes changed
What is a product?
the substances produced in a chemical reaction
What is an exothermic reaction?
A reaction where heat energy is released to its surroundings
What is an endothermic reaction?
A reaction where heat energy is absorbed into the reaction from its surroundings
in an endothermic reaction..
the reactants have less energy than the products
in an exothermic reaction..
the reactants hold more energy than the products
What are the four factors affecting reaction rate?
temperature, concentration, particle size, use of a catalyst
Rates of reactants can be measured by..
changes in the concentration of the reactants or products, changes in the mass of the reactants or products, changes in the volume of the reactants or products
Properties of electrons
mass of 0 a.m.u
found in the energy levels
have a charge of -1
properties of protons
have a mass of 1 a.m.u
found in the nucleus
have a charge of +1
Properties of a neutron
mass of 1 a.m.u
found in the nucleus
charge of 0
why does every atom have a neutral charge?
they have the same number of positive protons as negative electrons. These opposite charges cancel each other out making the atom neutral.
Why do elements in the same group have similar chemical properties?
because they have the same number of outer electrons and the same valency
Valency
the number of unpaired electrons in the outer electron shell of an atom
Alkali metals
Metals that are in group one of the periodic table, when reacted with water they become alkalis and produce hydrogen gas, the metals become more reactive as you go down the group
Halogens
elements in group 7 and as you go down the group they become less reactive
Noble gasses
Elements in group 8 and are very unreactive
What does the atomic number tell you?
the amount of protons and electrons in an element
how to calculate the mass number
m=p+n
how to calculate the number of neutrons
n=m-p
what is an isotope
an atom with the same atomic number but different mass numbers
why do atoms form bonds?
to achieve a stable electron arrangement
covalent bonding
A covalent bond is a shared pair of electrons between atoms of two non-metal elements.
properties of covalent network bonds
very high mp and bp, strong bonds, graphite, boron, silicon and carbon are examples
covalent molecular properties
usually liquids at room temperature, weak bonds, low mp and bp,
ionic bonding
the electrostatic force of attraction between a positively charged metal ion and a negatively charged non-metal ion.
pH scale
determines how acidic or alkaline a solution is
Acids pH
pH of less than 7
alkali pH
pH of more than 7
neutral solutions pH
pH of exactly 7 water is an example
What does the pH measure
the concentration of hydrogen ions in a solution
Alkalis
soluble bases and are formed when a metal oxide, metal carbonate or a metal hydroxide is dissolves in water
Acids
an acidic solution that is formed when a non metal oxide is dissolved in water
why can acidic and alkaline solutions conduct electricity?
because they have ions that are free to carry charge
equilibrium
water molecules breaking down hydroxide ions into hydrogen ions, a reversible reaction, present in all aqueous solutions
Acidic solutions contain
more hydrogen ions than hydroxide ions
Alkaline solutions contain
more hydroxide ions than hydrogen
what is neutralisation?
the reaction of an acid with a base that results in the pH moving towards 7
Equations for neutralisation
Acid+ alkali —-> salt+water
Acid+ metal oxide —–> salt+water
Naming Acids
the metal ion from the alkali (or base) replaces the hydrogen ion from the acid,
Hydrochloric acid+ sodium hydroxide —> sodium chloride+ water+ carbon dioxide
what is a spectator ion?
ions that are present during the reaction but are unchanged by the reaction
what is a titration used for?
to accurately measure the volume of acid and alkali that react in neutralisation reactions
known concentration in a titration
titrant
Difference between the starting volume and end volume in a titration
titre
pipette
allows you to add a precise amount of an acid or alkali to your empty conical flask
phenothaline
indicator that can be used in titrations
turns water from pink to clear again when solutions neutralised
how do you ensure accuracy during a titration
make sure conical flask is places under a white tile after indicator is added, this allows you to see the indicator clearly.
burette should not be filled above eyelevel to stop acid from tipping onto you and for an accurate measurement.
reading should be taken from the bottom of the meniscus
end point
the point in which the titration is neutralised and solution has turned from pink to clear
titration equation
when doing a titration repeat the experiment and take a note each time of the volume left to make sure the titre volume is consistent they should be within 0.2cm of each other
average titre = all titre volumes added together/ number of readings that were taken
rough volume not used to calculate average titre
concordant
titre results that are within 0.2cm of each other
Give 2 advantages of neutralising with a metal carbonate instead of a metal oxide
Reaction rate is high enough that acid doesn’t need to be heated
Easier end point detection due to evolution of CO2
What is a Base?
A substance that neutralises an acid
Why can acids never have zero OH- (aq) ions present?
Because acids are aqueous solutions and the dissociation of water means some OH- ions must be present
Why can alkalis never have zero H+ (aq) ions present
Because alkalis are aqueous solutions and the dissociation of water means some H+ ions must be present
