Chemistry: sept 11 Flashcards
How many decimal points should you measure a burette too
2 decimal points
what is the boiling point of water
100 degrees celsius
What element has the atomic number 20
Calcium
Define relative atomic mass
the ratio of the average mass of one atom of an element to one twelfth of the mass of an atom of carbon-12.
What term is used to describe an oxide that reacts with acids and alkalis
Amphoteric
What should a dot and cross diagram have
dots and crosses
Mole formula
N = m/mr
moles = mass/molecular mass
what is a spatula used for
Spatulas are used to transport and distribute dry chemical compounds
describe ionic compounds
It conducts electricity when dissolved in water
It has a high melting point due to strong attractive forces between ions
the ionic bonds are formed between metallic and non metallic elements
is this statement about oxides correct: Magnesium oxide reacts with nitric acid to make a salt
Yes
why are mixtures filtered
To remove the excess filtrate
Properties of ammonia (NH3)
colourless
less dense than air
uses of caustic soda (sodium hydroxide)
Drain cleaner
Fertiliser
What is Calcium carbonate used for (CaCO3)
Kitchen benches (when its marble)
how to make concrete
CaCO3 is broken down to CaO + CO2 which equals Ca(OH)2
dissolving
The process in which solvent molecules such as water surround solute particles such as ions
(like those in salt) or molecules (like those in sugar)
Are all nitrates, sodium, potassium and ammonium salts are soluble.
yes
What chlorides, bromides and iodides are not soluble
Pb2+, Cu+ and Ag+ are not soluble
how many flourides are soluble
All of them
What carbonates are soluble
The carbonates of alkali metals are soluble
The rest aren’t
What sulphates are soluble
Most sulphates are soluble, Ca2+ and Pb2+ are not Ag+
and Ba2+ are slightly soluble.
how to perform a flame test
- Dip a clean flame test loop in concentrated hydrochloric acid.
- Hold the flame test loop at the edge of a roaring bunsen burner flame and ensure the flame does not
change colour. If it does dip in acid again and repeat. - Dip the wire in the solid being testing picking up a few crystals and hold it at the edge of the roaring
Bunsen flame and observe the changed colour of the flame, and decide which metal it indicates. - Clean the loop in acid and rinse with water, then repeat steps 1 to 3 with a new sample.
Ion’s reaction in flames
Lithium (Li+) Red flame
Sodium (Na+) Orange/Yellow flame
Potassium (K+) Lilac flame
Copper(II) (Cu2+) Blue/Green flame
Non metal oxides are
acids
Metal oxide + acid =
salt + water
Metal oxides are
bases
What does hydrated mean
it has water in it
Aqueous ammonia is added to a solution of a salt. A white precipitate is formed which dissolves in an
excess of aqueous ammonia. Which metal is in the salt?
Zinc
Two aqueous solutions, X and Y, are mixed together. What pair would not give
a white precipitate?
Magnesium nitrate and sodium sulphate
Dilute hydrochloric acid was added to a tube containing a unknown powder. There was a vigorous
reaction and a gas was produced which turned lime water cloudy. After the reaction stopped, excess
aqueous sodium hydroxide was added to the tube and a green gelatinous precipitate was formed.
What was the unknown powder.
FeCO3
When aqueous ammonium chloride was heated with aqueous Y, a gas which turned universal
indicator paper blue was evolved. Which ion must have been present in Y?
OH-
What is a fuel
something with stored chemical energy
What does exothermic mean
gives out heat
What does delta H =
enthalpy change
What is the symbol for delta
▵
What does EA mean
Activation energy
why do you need activation energy
to make stuff react
What is the unit of Enthalpy change
KJmol-1
Formula for amount of energy
energy (j) = heat capacity x mass x change in temp
The collision theory
If two particles hit each other at high energy in the right orientation you get a reaction
How does temperature affect rate of reaction
High temperature increases frequency and success
How does surface area affect rate of reaction
larger surface area increases frequency of collisions
How does concentration affect rate of reaction
Higher concentration increases frequency of collisions
How does a catalyst affect rate of reaction
Increase a rate of reaction without being consumed, increases the success of collisions
what increases frequency of collisions
Temperature
Surface area
Concentration
Pressure
What increases success of collisions
Temperature
catalyst
How to speed reaction
warming it
Increasing pressure (only gas)
increasing concentration
Using a catalyst
How does change in concentration affect equilibrium
If the concentration of one side of the equation is lowered for some reason, then the equation will shift so more is made to replace that which is lost. If the concentration of one side is increased, then that side will react quickly to get rid of the excess and restore the equilibrium to what it was.
how does change in temperature affect equilibrium
A change in temperature will affect the equilibrium depending on which direction on the equilibrium
is more exothermic. Le Chatelier’s principle applies to a change in temperature because the reversible
reaction would be exothermic in one direction and endothermic in the other, so an increase in
temperature would mean that the endothermic reaction would be favoured and vice versa. If the
temperature is raised, the equilibrium would shift so the less exothermic reaction would occur more
and so the temperature would try to fall. If the temperature were lowered, then the equilibrium would
shift so the more exothermic reaction would occur more and create ore of the substance at that end of
the equation.
How does change in pressure affect equilibrium
If the equation is off gasses and has different numbers of molecules on both sides, the equilibrium would shift so the pressure could be restored back to what it was.
How does adding a catalyst affect equilibrium
The addition of a catalyst does not change the concentrations of reactants or products. It does speed up the reaction rate in both forward and reverse directions and allows the system to reach equilibrium
more rapidly.
what does homogeneous mean
A substance is homogeneous if its composition is identical wherever you sample it - it has uniform composition and properties throughout.
what does dynamic mean
In chemistry, and in physics, a dynamic equilibrium exists once a reversible reaction occurs. Substances transition between the reactants and products at equal rates, meaning there is no net change.
what does equilibrium mean
Chemical equilibrium, condition in the course of a reversible chemical reaction in which no net change in the amounts of reactants and products occurs. A reversible chemical reaction is one in which the products, as soon as they are formed, react to produce the original reactants.
