Chemistry paper 2

Question 1

what is group 1

Answer 1

alkali metals

Question 2

what are the properties of group 1 metals

Answer 2

• all have one outer shell electron
• low melting and boiling points
• very soft
• form ionic compounds (+1 ion)

Question 3

why don’t group 1 elements form covalent bonds

Answer 3

they lose their outer shell electron so easily that sharing is necessary

Question 4

what happens with reactivity in group one

Answer 4

as you go down the group, they get more reactive because the outer electron is more easily lost because its further from the nucleus so there is a larger atomic radius so is less strongly attracted to the nucleus and less energy is needed to remove it

Question 5

what happens when the alkali metals are put in water

Answer 5

they react vigorously
the reaction produces hydrogen gas and a hydroxide of the metal

lithium will move around the surface fizzing
sodium and potassium do the same and also melt in the heat of the reaction. Potassium even gets hot enough to ignite the hydrogen gas being produced
caesium and rubidium do the same but explode

Question 6

what are the group seven elements known as

Answer 6

the halogens

Question 7

what do the halogens exist as

Answer 7

diatomic molecules

Question 8

what are the properties of group 7 elements

Answer 8

as you go down melting and boiling points increase

Question 9

what is the state and colour of chlorine, bromine and iodine at room temperature

Answer 9

chlorine - fairly reactive poisonous green gas
bromine - poisonous red-brown liquid which gives off an orange vapour at room temperature
iodine - a dark grey crystalline solid which gives off a purple vapour when heated

Question 10

what is the test for chlorine

Answer 10

damp blue litmus paper will turn red then bleach white

Question 11

what happens to reactivity in group 7

Answer 11

reactivity decreases as you go down because there is a larger atomic radius and therefore more electron shielding so it is harder for the atom to attract the one electron it needs because the force of electrostatic attraction between the nucleus and new electron is weak

they form 1- ions

Question 12

what happens when the halogens react with metals

Answer 12

they form a salt called a metal halide

e.g sodium + chlorine -> sodium chloride

Question 13

what happens when halides react with hydrogen

Answer 13

form hydrogen halides
they are soluble (can dissolve in water) to from acidic solutions
e.g HCL forms hydrochloric acid in water

Question 14

what are the halogen displacement reactions

Answer 14

redox reactions

the halogens gain electrons (reduction) whilst halide ions lose electrons (oxidation)

Question 15

how would you do a displacement reactions to show the reactivity trend of the halogens

Answer 15

1) start by measuring out a 5ml of halide salt solution in a test tube
2) add a few drops of halogen solution to it and gently shake tube
3) if you see a colour change then a reaction has happened - the halogen has displaced the halide ions from the salt
4) repeat the process using the different combinations of halide salt and halogen

Question 16

what is group zero

Answer 16

the noble gases

Question 17

what are the properties of the noble gases

Answer 17

• colourless gas at room temperature
• monatomic (single atoms not molecules)
• more or less inert - they don’t react with much at all because they have a full outer shell of electrons so they don’t give up or gain electrons easily
• non-flammable
• hard to observe so took a long time to discover

Question 18

what are the everyday uses of the noble gases

Answer 18

• provide an inert atmosphere
• argon in filament lamps because it is non-flammable it stops the very hot filament from burning away
• flash photography uses the above principle with argon, krypton and Zenon to prevent high temperature flashes in filaments
• argon and helium can be used to protect metals that are being welded as the inert atmosphere stops the hot metal reacting with oxygen
• helium is used in airships and party balloons because it has a lower density than air so it floats and is non-flammable so safer to use than hydrogen gas

Question 19

what are the properties of the noble gases

Answer 19

• boiling, melting point and density all increase as you go down the group

Question 20

what is the rate of reaction

Answer 20

how quickly a reaction happens, how quickly a product is formed or the reactants are used up

Question 21

what is the formula for rate of reaction

Answer 21

amount of reactant used or product formed / time

Question 22

what are three ways that you can measure the rate of reaction

Answer 22

• precipitation
• change in mass (usually gas given off)
• the volume of gas given off

Question 23

how does precipitation measure the rate of reaction

Answer 23

• mixing two see-through solutions produces a precipitate which clouds the solution
• you mix the two reactant solutions and put the flask on a piece of paper that has a mark on it
• observe the mark through the mixture and measure how long it takes for the mark to be obscured. The faster it disappears, the faster the reaction

Question 24

why is using precipitation to measure the rate of reaction not accurate

Answer 24

because the result is subjective - different people might not agree on exactly when the mark disappears

Question 25

how does a change in mass (usually gas given off) measure the rate of reaction

Answer 25

- measure the rate of reaction that produces a gas using a mass balance - as the gas is released, the lost mass is easily measured on the balance - the quicker the reading on the balance drops, the faster the reaction - when the mass balance stops changing the reaction has stopped - plot a graph of change in mass against time

Question 26

what safety precautions should you take when using a change in mass by gas given off to measure the rate of reaction

Answer 26

this method releases the gas straight into the room so if the gas is harmful you must do the experiment in a fume cupboard

Question 27

how can you measure the rate of reaction by the volume of gas given off

Answer 27

- use gas syringe to measure volume of gas given off - the more gas given off during a set time interval, the faster the reaction - you can tell the reaction has finished when no more gas is produced - plot a graph of gas volume against time elapsed

Question 28

what must you be careful of when using the volume of gas given off to measure the rate of reaction

Answer 28

you need to be careful that you're using the right size gas syringe for your experiment because if the reaction is too vigorous, you can blow the plunger out of the end of the syringe

Question 29

how can you measure how surface area affects the rate of reaction

Answer 29

using marble chips and hydrochloric acid 1) measure volume of gas produced using a gas syringe. take readings at regular time intervals and record results in a table 2) plot graph (time is x axis and volume is y axis) 3) repeat the experiment with the same volume and conc of acid and same mass of marble chips but with the chips more crunched up 4) then repeat with the same mass of powdered chalk

Question 30

what does using finer particles mean for surface area

Answer 30

finer particles means that the marble has a larger surface area

Question 31

how can you measure the effect of temperature on the rate of reaction

Answer 31

sodium thiosulfate and hydrochloric acid are both clear, colourless solutions and react to form a yellow precipitate of sulphur - measure 25ml of both liquids using measuring cylinder - use a water bath to gently heat both solutions to 10 degrees before you mix them - mix solutions in a conical flask placed on a piece of paper with a cross on it - watch the black mark disappear through the cloudy, yellow sulphur and time how long it takes to go - the reaction is then repeated at 20 and 30 degrees - depth and volume and concentrations of the liquids must be the same the shorter the length of time taken for the mark to be obscured, the faster the rate

Question 32

what is activation energy

Answer 32

the minimum energy that particles need to react when they collide particles need to collide with at least the activation energy for the collision to be successful

Question 33

what five factors affect the rate of reaction

Answer 33

- temperature - pressure - concentration - catalyst - surface area

Question 34

how can you follow a change in temperature of a reaction mixture

Answer 34

- put a polystyrene cup into a large beaker of cotton wool for insulation to help limit energy transfer to or from the reaction mixture - add 20ml of first reagent to the cup - measure the initial temperature of the solution - add 20ml of you second reagent and stir the reaction mixture - put a lid on the cup to reduce any energy lost by evaporation - record the maximum or minimum temperature that the mixture reaches during the reaction - calculate the temperature change