A sequence of chemicals

Question 1

how was the sample of copper initially weighed

Answer 1

1) weigh and tar the 250 mL beaker

2) add the cu(s) to the beaker to find the mass

Question 2

how much nitric acid was added to a 100 mL graduated cylinder

Answer 2

10 mL

Question 3

what are a safety note about nitric acid

Answer 3

causes severe burns

vapours irritate respiratory system, eyes and skin

Question 4

how was part A of the experiment completed

Answer 4

add the 10 mL of nitric acid to the weighed copper and record the observations

• the solution colour is from Cu(NO3)2
• fumes are nitrogen dioxide

Question 5

what can the reaction from part a be described as

Answer 5

oxidation dissolution as the copper is being oxidized in the process

Question 6

how was part b of the solution done

Answer 6

a few mL of RO water is added to the solution which results in the solution changing colour

Question 7

why does the part B step change colour

Answer 7

due to hydrated CU(II) ions

Cu(H2O)6 +2

Question 8

how was the NaOH required for step C prepared

Answer 8

6 g of the solid NaOH was weighed and added to 25 mL of RO water

• this preparation is done in an ice bath because it is a VERY exothermic reaction

Question 9

how was step C completed

Answer 9

the created 6 M NaOH solution was carefully added to the Cu(OH2)6 solution while stirring slowly

Question 10

what was the expected product of step C

Answer 10

Copper (II) hydroxide

Cu(OH)2

Question 11

what does a teal-coloured thin suspension after step C mean

Answer 11

you had to add more 6 M NaOH to the copper solution for the correct product

Question 12

how was Step d completed in this experiment

Answer 12

• 100 mL of RO water was added to the copper solution
• stirring constantly the copper solution was brought to a gentle boil for a good 10 mins or so
• use a Buchner funnel to filter the copper solution through
• wash the copper on the filter paper TWICE with 30 mL of RO water
• after discarding of the waste water, wash the copper on the filter paper ONCE with 25 mL acetone

Question 13

where does the acetone used to rinse the CuO on the filter paper go after use

Answer 13

down the non-halogenated organic waste container

Question 14

how was step E completed

Answer 14

• 25mL of 3 M H2SO4 to the CuO while stirring so all the copper becomes CuSO4

Question 15

how was the 3 M H2SO4 prepared for step E of the experiment

Answer 15

add 6 mL of the acid to 30 mL of water to form 36 mL of the diluted acid

Question 16

how much zinc was added during step F and how many times

Answer 16

up to 3 times of 0.5 grams of zinc was added to the CuSO4 solution

Question 17

how was excess zinc removed from the beaker during step F and WHY

Answer 17

add 10 mL of RO water and 5 mL of 3 M H2SO4 to the beaker and mix with a stir rod

the zinc will react with the aqueous strong acid to produce H2 gas while the 3 M H2SO4 will NOT attack the copper metal but it WILL dissolve the zinc metal

Question 18

how was the resulting copper from step F extracted from the solution

Answer 18

set up a Buchner funnel
- wash copper twice with 25 mL RO water
- wash copper twice with 25 mL acetone

Question 19

how long was the copper placed in the oven for

Answer 19

about 15 mins

Question 20

how was the recovered percent of copper done

Answer 20

• once the copper has been washed the required times in the Buchner funnel, it was added to a PRE-WEIGHED beaker and placed in the oven for 15 mins
• after the beaker has cooled, weight it again WITH the copper in it and determine the mass of the copper
• divide the INITIAL mass of the copper by the RECOVERED mass ( and multiply by 100) to determine percent copper recovered

Question 21

what happened when the solid copper was mixed with the HNO3 in step A

Answer 21

the copper turned from brown to dark green AND a brown gas was seen emerging off of the solution surface

Question 22

what happened when a few mL of RO water was added to the solution from part A (with the CU(NO3)2)

Answer 22

the solution turned from dark green to teal before ENDING in a dark blue

Question 23

what happened when the Cu(OH2)6 solution reacted with NaOH in step C

Answer 23

reaction took place in the ice bath and the copper solution turned from blue to BLACK

Question 24

what was noticed as the black copper (ii) hydroxide was heated

Answer 24

a solid precipitate was formed within the solution

Question 25

what was produced during the heating stage of part D

Answer 25

CuO(s) and water

Question 26

what happened when the CuO reacted with H2SO4

Answer 26

all the black solid was dissolved and the colour changed from black back to BLUE

Question 27

what happened when the zinc was added to the CuSO4

Answer 27

the reaction was immediate and the colour changed to a copper-brownw

Question 28

what was the copper solid appearance like after heating

Answer 28

was less saturated and more a reddish brown colour

Question 29

what is the balanced chemical reaction for Step A

Answer 29

Cu(s) + 4 HNO3(aq) ——-> Cu(NO3)2 (aq) + 2 NO2(g) + 2 H2O (l)

Question 30

what is the balanced chemical reaction for Step B

Answer 30

Cu(NO3)2 (aq) + 6H2O (l) ——-> Cu(OH2)6 ^2+ (aq) + 2NO3-(aq)

Question 31

what is the balanced chemical reaction for Step C

Answer 31

Cu(OH2)6 (aq) + 2NaOH (aq) ——>Cu(OH)2 (s) + 6 H2O (l) + 2Na+ (aq)

Question 32

what is the balanced chemical reaction for Step D

Answer 32

Cu(OH)2 (s) + heat —–> CuO(s) + H2O(l)

Question 33

what is the balanced chemical reaction for Step E

Answer 33

CuO(s) + H2SO4 (aq) ——>CuSO4 (aq) + H2O (l)

Question 34

what is the balanced chemical reaction for Step F

Answer 34

CuSO4(aq) + Zn(s) ——-> ZnSO4 (aq) + Cu(s)