Unit 5 :P

Question 1

What is the test and positive observations for the halogens?

Answer 1

Reflux with NaOH(aq) and add AgNO3 (aq).
Cl- will give a white ppt
Br- will give a cream ppt
I- will give a yellow ppt

Question 2

What are the group 2 metal ions reactions with NH4+?

Answer 2

Mg2+ - white ppt of Mg(OH)2 formed
Ca2+ - no observable change
Sr2+ - no observable change
Ba+ - no observable change

Question 3

What are the group 2 metal ions reactions with excess OH-?

Answer 3

Mg2+ - white ppt of Mg(OH)2 formed
Ca2+ - white ppt of Ca(OH)2 formed
Sr2+ - slight white ppt of Sr(OH)2
Ba2+ - no observable change

Question 4

What are the group 2 metal ions reactions with excess SO4-?

Answer 4

Mg2+ - colourless solution formed
Ca2+ - slight white ppt of CaSO4 formed
Sr2+ - white ppt of SrSO4 formed
Ba2+ - white ppt of BaSO4 formed

Question 5

What is the test for CO3^2-?

Answer 5

Add dilute HCl and pipette the gas formed into limewater. The limewater should turn milky when the gas is bubbled through.

Question 6

What are the observations of the different metals for the flame test?

Answer 6

K+ - lilac flame
Na+ - yellow/orange flame
Ca2+ - brick red flame
Li+ - red flame
Ba+ - apple green flame
Mg2+ - no colour
Sr2+ - crimson red

Question 7

What are the observations of the different metals for the flame test?

Answer 7

K+ - lilac flame
Na+ - yellow/orange flame
Ca2+ - brick red flame
Li+ - red flame
Ba+ - apple green flame
Mg2+ - no colour
Sr2+ - crimson red

Question 8

What is the test for carboxylic acids?

Answer 8

Blue litmus paper turns red. Adding NaHCO3 will produce effervescence and bubbles of CO2.

Question 9

What is the test for amines?

Answer 9

Red litmus paper turns blue.

Question 10

What is the test for amides?

Answer 10

Alkaline hydrolysis, OH-/H2O produces NH3 gas.

Question 11

What is a further test for identifying the halogens?

Answer 11

Add NH3 to precipitates after the AgNO3 test.
Cl- - dissolves in dilute NH3
Br- - dissolves in concentrated NH3
I- - does not dissolve in NH3

Question 12

What are some reactions of Pb2+?

Answer 12

OH- (aq) - white ppt of Pb(OH)2 formed
xs OH- (aq) - ppt redissolves to form [Pb(OH)4]2-
Cl- (aq) - dense white ppt of PbCl2 formed
I- (aq) - dense yellow ppt of PbI2 formed

Question 13

What are the observations when H2SO4 is added to a sodium halide?

Answer 13

NaCl- steamy fumes of HCl are produced
NaBr- steamy fumes of HBr and orange fumes of Br2 are produced
NaI- steamy fumes of HI, purple fumes of I2, rotten egg smell of H2S and a yellow solid of S is produced

Question 14

What colour is [Fe(H2O)6]2+?

Answer 14

Pale green.

Question 15

What colour is [Fe(H2O)6]3+?

Answer 15

Yellow.

Question 16

What colour is [Cu(H2O)6]2+?

Answer 16

Blue.

Question 17

What colour is [Cr(H2O)6]3+?

Answer 17

Dark green.

Question 18

What colour is [Co(H2O)6]2+?

Answer 18

Pink.

Question 19

What colour is [Co(H2O)6]2+?

Answer 19

Pink.

Question 20

What colour is [Cu(NH3)2(H2O)4]2+?

Answer 20

Royal blue.

Question 21

What colour is [CuCl4]2-?

Answer 21

Yellow/green.

Question 22

What colour is [CoCl4]2-?

Answer 22

Blue.

Question 23

What is observed when OH- and excess OH- is added to [Cr(H2O)6]3+?

Answer 23

OH- - grey green ppt of [Cr(H2O)3(OH)3]
xs OH- - ppt dissolves to deep green [Cr(OH)6]3-

Question 24

What is observed when OH- and excess OH- is added to [Cr(H2O)6]3+?

Answer 24

OH- - grey green ppt of [Cr(H2O)3(OH)3]
xs OH- - ppt dissolves to deep green [Cr(OH)6]3-

Question 25

What is observed when OH- and excess OH- is added to [Fe(H2O)6]2+?

Answer 25

OH- - dark green ppt of [Fe(H2O)4(OH)2] xs OH- - red-brown colour due to oxidation

Question 26

What is observed when OH- and excess OH- is added to [Fe(H2O)6]3+?

Answer 26

OH- - red-brown ppt of [Fe(H2O)3(OH)3] xs OH- - no further reaction

Question 27

What is observed when OH- and excess OH- is added to [Cu(H2O)6]2+?

Answer 27

OH- - pale blue ppt of [Cu(H2O)4(OH)2] xs OH- - no further reaction

Question 28

What is the property of all group one salts?

Answer 28

They are all soluble.

Question 29

What is the property of group two carbonates?

Answer 29

They are all insoluble.

Question 30

Which is more reactive, group one or two?

Answer 30

Group one.

Question 31

How does reactivity change down group one and two?

Answer 31

It increases.

Question 32

How does reactivity change down group seven?

Answer 32

It decreases.

Question 33

What is calorimetry?

Answer 33

The measurement enthalpy changes in chemical reactions.

Question 34

What are the calculations for enthalpy change?

Answer 34

q= mcΔT and ΔH= -mcΔT/n

Question 35

Label the terms in q=mcΔT

Answer 35

q= heat transferred in J m= mass of water in g c= specific heat capacity of water in Jg-1C-1 ΔT= temp change in C

Question 36

Describe the determination of an enthalpy change of combustion

Answer 36

1. Allow a suitable gap between the base of the metal container and the top of the spirit burner. 2. Accurately measure the amount of water being added to the metal container. 3. Use an accurate thermometer to measure the initial temperature of the water, and record the temperature when a steady value has been obtained. 4. Weigh spirit burner and record initial mass. 5. Allow the fuel to heat the water to a suitable temperature. 6. Extinguish the flame and record the final temperature, and weigh the final mass of the spirit burner.

Question 37

Why might the value obtained be low in the direct determination of enthalpy change of combustion?

Answer 37

Some of the energy transferred from the burning fuel is lost to heating the apparatus and the surroundings, and the fuel may not be completely combusted.

Question 38

Describe the indirect determination of an enthalpy change?

Answer 38

1. Measure a volume of acid using a burette or pipette and place it in the cup (must be in excess). 2. Use a thermometer to measure the initial temperature of the acid, and record the temperature once a steady value has been obtained. 3. Accurately weigh the solid in powder form (to ensure as rapid of a reaction as possible) in a suitable container. 4. Add all the solid in the cup, stir the mixture and start a stopwatch. 5. Keep stirring with the thermometer and record the temperature regularly, stopping when it has fallen for five minutes. 6. Plot a graph of temperature over time to calculate the maximum temperature the mixture might have reached. 7. Calculate the amount of heat transferred, the enthalpy change and use Hess's law to calculate the required enthalpy change.

Question 39

Why might the value obtained be low in the indirect determination of enthalpy change?

Answer 39

Due to the simple type of calorimeter used.

Question 40

How to calculate % yield?

Answer 40

(Mass of product obtained/ maximum theoretical mass of product) x100

Question 41

Why might a reaction not produce the maximum amount of product?

Answer 41

-The reaction may be reversible - Side reactions may be occurring - Product lost in transfer

Question 42

How to calculate atom economy?

Answer 42

(Mr of desired product/ Mr of all reactants) x100

Question 43

What is observed when Cl displaces Br?

Answer 43

A colourless to yellow colour change is observed.

Question 44

What is observed when Cl or Br displaces I?

Answer 44

A colourless to brown colour change is observed.

Question 45

How to convert from J to KJ?

Answer 45

Divide by 1000.