REQUIRED PRACTICALS P1

Question 1

Describe a method to make pure, dry crystal of magnesium sulphate from a metal oxide and a dilute acid.

Answer 1

use magnesium oxide and sulphuric acid
add a fixed volume of sulphuric acid to a beaker and gently heat the acid
add magnesium oxide with a spatula and stir using a glass rod
continue adding magnesium oxide until the magnesium oxide is in excess
you should then filter the solution using a filter paper and funnel to remove excess magnesium oxide
heat the solution in an evaporating basin to until you start seeing crystal to form
turn off the heat and leave the solution to dry
pat the crystals dry with filter paper

Question 2

carrying out a titration

Answer 2

use pipette to transfer 25cm3 of sodium hydroxide solution into a conical flask
add 5 drops of indicator for example phenol Phalen or methyl orange to the sodium hydroxide in the conical flask
place the conical flask on a white tile, so we see a colour change more clearly
fill a burette with sulfuric acid
start adding acid into the conical flask until we see a colour change, do this while swirling the flask
stop swirling flask and adding acid when you see a colour change for phenophalen pink to colourless for methyl orange yellow to red
read volume of acid added from burette
repeat titration several times until you get readings 0.1cm3 of each other

Question 3

what are the colour changes fro phenophelon

Answer 3

pink to colourless

Question 4

what is the colour change for methyl orange

Answer 4

yellow to red

Question 5

explain why the student should use a pipette to measure the dilute sulphuric acid and a burette to measure the sodium hydroxide solution

Answer 5

pipette measures fixed volume but a burette measure variable volume

Question 6

test for hydrogen

Answer 6

wooden splint squeaky pop in test tube

Question 7

test for oxy

Answer 7

glowing splint relights in test tube

Question 8

test for co2

Answer 8

turns limewater cloudy

Question 9

test for chlorine

Answer 9

turns damp blue litmus paper red

Question 10

whats filtration used for

Answer 10

separate insoluble solid from aliquid

Question 11

temp change practical

Answer 11

use a measuring cyclinder to measure 30cm3 of dilute hydrochloric acid
transfer acid into polystyrene cup
use thermometer to measure the temp of the acid
record this on results table
use measuring cylinder to measure 5cm3 of sodium hydroxide solution and we transfer this to polystyrene cup
place plastic lid over cup with thermometer through middle
gently stir solution using thermometer
look at the temp rise when it stops changing, record the highest temperature reached
rinse out polystyrene cup so that we can repeat experiment using 10cm3 of sodium hydroxide solution
carry out experiment several more times and increase volume of sodium hydroxide solution by 5cm3
repeat whole experiment twice

Question 12

iv of temp prac

Answer 12

volume of sodium hydroxide

Question 13

dv of temp prac

Answer 13

max temp reached

Question 14

cv of temp prac

Answer 14

volume of hydrochloric acid

Question 15

why do you use polystyrene cup

Answer 15

the experiment we are measuring the temp, this means that we want to reduce heat loss, polystyrene cup is a good insulator so this reduces heat loss

Question 16

electrolysis of copper chloride

Answer 16

add 50cm of copper chlrodie to 100cm3 beaker
insert carbon electrodes into solution
collect the electrodes to a 4v power supply
look at the two electrodes
cathode gets coated with copper because copper is less reactive than hydrogen so copper is discharged at the cathode
at positive electrode, the anode bubbles of gas are produced
as chloride is a halide ion it is discharged at the anode
so chlorine gas produced at the anode

Question 17

electrolysis of sodium chloride

Answer 17

add 50cm of sodium chloride to 100cm3 beaker
insert carbon electrodes into solution
collect the electrodes to a 4v power supply
look at the two electrodes
cathode bubbles of gas are produced this is because sodium is more reactive than hydrogen so hydrogen is discharged at the cathode
at positive electrode, the anode bubbles of gas are produced
as chloride is a halide ion it is discharged at the anode
so chlorine gas produced at the anode

Question 18

titration calculations

Answer 18

write underneath what they have given you in the queation n c v
that stands for moles concentration and volume
fill in what they give you in the question
find out what they want so moles of one of them- moles = concentration * volume
see how many moles the acid or alkali has (the big number at the front) and adjust answer If needed
find out concentration of one of them - moles/volume

Question 19

if asked to find g/dm3 how would you do that

Answer 19

get your answer which is in mol/dm3 at times it by the mr given

Question 20

before starting the question what should you always do to the volume which is in cm3

Answer 20

change it to dm3 by dividing it by 1000

Question 21

cm3 to dm3

Answer 21

divide b 1000

Question 22

how do you see how many moles

Answer 22

look at the front of the substance

if theres no number in front it hass one mole

Question 23

moles=

Answer 23

concentration * volume

Question 24

concentration =

Answer 24

moles/volume

Question 25

when doing a titration calculation and they giving you a table what should you do

Answer 25

take the three concordant results (the results within 0.1 of each other) and calculate the mean of that and use that as the volume in the calcualtion