chem term 2

Question 1

test for hydrogen

Answer 1

Use​ ​a​ ​burning​ ​splint​ ​held​ ​at​ ​the​ ​open​ ​end​ ​of​ ​a​ ​test​ ​tube​ ​of​ ​the​ ​gas
▪ Creates​ ​a​ ​‘squeaky​ ​pop’​ ​sound

Question 2

test for oxygen

Answer 2

Uses​ ​a​ ​glowing​ ​splint​ ​inserted​ ​into​ ​a​ ​test​ ​tube​ ​of​ ​the​ ​gas
▪ Splint​ ​relights​ ​in​ ​oxygen

Question 3

test for carbon dioxide

Answer 3

Bubble​ ​the​ ​gas​ ​through​ ​the​ ​limewater​ ​and​ ​it​ ​will​ ​turn milky​ ​(cloudy)

Question 4

test for ammonia

Answer 4

Makes​ ​damp​ ​red​ ​litmus​ ​paper​ ​turn​ ​blue
o Forms​ ​a​ ​white​ ​smoke​ ​of​ ​ammonium​ ​chloride​ ​when​ ​hydrogen​ ​chloride

Question 5

test for chlorine

Answer 5

When​ ​damp​ ​litmus​ ​paper​ ​is​ ​put​ ​into​ ​chlorine​ ​gas​ ​the​ ​litmus​ ​paper​ ​is bleached​ ​and​ ​turns​ ​white

Question 6

describe how to carry out a flame test

Answer 6

take​ ​a​ ​sample​ ​of​ ​the​ ​metal​ ​on​ ​a​ ​wire​ ​and​ ​put​ ​it​ ​in​ ​a​ ​flame,​ ​the​ ​flame​ ​will​ ​turn​ ​a specific​ ​colour,​ ​showing​ ​what​ ​metal​ ​it​ ​is

Question 7

flame test for Li+

Answer 7

lithium=red

Question 8

flame test for Na+

Answer 8

sodium=yellow

Question 9

flame test for K+

Answer 9

potassium=lilac

Question 10

flame test for Ca+

Answer 10

calcium=orange red

Question 11

flame test for cu2+

Answer 11

copper= blue green

Question 12

tests for halide ions

Answer 12

First​ ​add​ ​dilute​ ​nitric​ ​acid,​ ​followed​ ​by​ ​silver​ ​nitrate​ ​solution o Chloride​ ​gives​ ​a​ ​white​ ​precipitate
o Bromide​ ​gives​ ​a​ cream precipitate
o Iodine​ ​gives​ ​a​ yellow precipitate

Question 13

test for sulfate ions

Answer 13

o First​ ​add​ ​dilute​ ​hydrochloric​ ​acid,​ ​followed​ ​by​ ​barium​ ​chloride​ ​solution
o A​ ​white​ ​precipitate​ ​will​ ​form​ ​when​ ​sulfate​ ​ions​ ​are​ ​in​ ​this​ ​solution

Question 14

test for carbonate ions

Answer 14

o Carbonates​ ​react​ ​with​ ​dilute​ ​acids​ ​to​ ​create​ ​carbon​ ​dioxide.
o This​ ​gas​ ​can​ ​be​ ​bubbled​ ​through​ ​limewater,​ ​if​ ​the​ ​limewater​ ​goes​ ​cloudy, the​ ​gas​ ​is​ ​CO2​ .​

Question 15

test for the presence of water using anhydrous copper sulphate

Answer 15

● Anhydrous​ ​copper(II)​ ​sulfate​ ​is​ ​white
o When​ ​water​ ​is​ ​present,​ ​it​​ ​turns​ ​blue

Question 16

describe​ ​a​ ​physical​ ​test​ ​to​ ​show​ ​whether​ ​a​ ​sample​ ​of​ ​water​ ​is​ ​pure

Answer 16

The​ ​purity​ ​of​ ​water​ ​can​ ​be​ ​tested​ ​by​ ​evaporating​ ​it​ ​on​ ​an​ ​evaporating​ ​dish​ ​or​ ​by measuring​ ​its​ ​boiling​ ​point

Question 17

what is an exothermic reaction

Answer 17

An​ ​exothermic​ ​reaction​ ​is​ ​one​ ​that​ ​transfers​ ​energy​ ​to​ ​the​ ​surroundings so​ ​the​ ​temperature​ ​of​ ​the​ ​surroundings​ ​increases.
● Examples​ ​of​ ​exothermic​ ​reactions​ ​include;​ ​combustion

Question 18

what is an endothermic reaction

Answer 18

An​ ​endothermic​ ​reaction​ ​is​ ​one​ ​that​ ​takes​ ​in​ ​energy​ ​from the​ ​surroundings​ ​so​ ​the​ ​temperature​ ​of​ ​the​ ​surroundings decreases.

Question 19

describe simple calorimetry experiments

Answer 19

● Salts​ ​dissolving​ ​in​ ​water​ ​can​ ​be​ ​either​ ​exothermic​ ​or​ ​endothermic
● Neutralisation​ ​reaction​ ​is​ ​exothermic
● Displacement​ ​is​ ​an​ ​exothermic​ ​or​ ​endothermic​ ​reaction
● Combustion​ ​is​ ​an​ ​exothermic​ ​reaction

Question 20

increasing temp in a reaction

Answer 20

Increasing​ ​the​ ​temperature​ ​increases​ ​the rate​ ​of​ ​reaction.​ ​As​ ​increasing​ ​temperature increases​ ​the​ ​speed​ ​of​ ​the​ ​moving​ ​particles,​ ​so they​ ​collide​ ​more​ ​frequently​ ​and​ ​energetically.

Question 21

increasing pressure in a reaction

Answer 21

ncreasing​ ​pressure​ ​in​ ​reacting​ ​gases increases​ ​the​ ​rate​ ​of​ ​reaction,​ ​as​ ​it​ ​increases​ ​the​ ​frequency​ ​of​ ​collisions.

Question 22

increased conc in a reaction

Answer 22

Increasing​ ​concentration​ ​of​ ​reacting​ ​solutions​ ​increases​ ​the​ ​rate​ ​of​ ​reaction,​ ​as it​ ​increases​ ​the​ ​frequency​ ​of​ ​collisions.

Question 23

increased surface area in a reaction

Answer 23

Increasing​ ​the​ ​surface​ ​area​ ​of​ ​solid​ ​reactants​ ​increases​ ​the​ ​rate​ ​of​ ​reaction,​ ​as​ ​it increases​ ​the​ ​frequency​ ​of​ ​collisions.

Question 24

what is a catalyst

Answer 24

Catalysts​ ​are​ ​substances​ ​that​ ​speed​ ​up​ ​chemical​ ​reactions​ ​without​ ​being
changed​ ​or​ ​used​ ​up​ ​during​ ​the​ ​reaction

Question 25

know that a catalyst works by creating an alternative pathway

Answer 25

● Catalysts​ ​provide​ ​an​ ​alternative​ ​pathway​ ​for​ ​a​ ​chemical​ ​reaction​ ​with​ ​a​ ​lower activation​ ​energy.
● this​ ​increases​ ​the​ ​proportion​ ​of​ ​particles​ ​with​ ​energy​ ​to​ ​react.

Question 26

Know that some reactions are reversible and this is indicated by the symbol ⇌ in equations

Answer 26

● In​ ​some​ ​chemical​ ​reactions,​ ​the​ ​products​ ​of​ ​the​ ​reaction​ ​can​ ​react​ ​to​ ​produce the​ ​original​ ​reactants
o These​ ​are​ ​called​ ​reversible​ ​reactions
o The​ ​direction​ ​of​ ​the​ ​reaction​ ​can​ ​be​ ​changed​ ​by​ ​changing​ ​the​ ​conditions

Question 27

dehydration of hydrated copper(11) sulphate

Answer 27

○ Anhydrous​ ​copper(II)​ ​sulfate​ ​+​ ​water​ ​⇌​ ​hydrated​ ​copper(II)​ ​sulfate
○ White​ ​solid​ ​turns​ ​blue​ ​in​ ​presence​ ​of​ ​water
○ Forward​ ​reaction​ ​add​ ​water
○ Reverse​ ​reaction​ ​heat​ ​the​ ​hydrated​ ​copper(II)​ ​sulfate​ ​(water​ ​evaporates)

Question 28

Effect​ ​of​ ​heat​ ​on​ ​ammonium​ ​chloride

Answer 28

○ Ammonium​ ​chloride​ ​⇌​ ​ammonia​ ​+​ ​hydrogen​ ​chloride
○ The​ ​white​ ​solid​ ​(ammonium​ ​chloride)​ ​breaks​ ​down​ ​into​ ​ammonia​ ​and
hydrogen​ ​chloride​ ​(colourless​ ​gases)​ ​using​ ​heat
○ These​ ​gases​ ​can​ ​then​ ​react​ ​to​ ​form​ ​ammonium​ ​chloride