Some chemistry questions

arkszhi SG

Hello, I have a couple of chemistry questions. Hope I can get some answers before tomorrow's exams. Please kindly explain why the answer is such.

1. Which of the following would produce bubbles of gas at each electrode, when electrolysed using platinum electrodes?

a) Copper(II) sulphate solution

b) Silver nitrate solution

c) Lithium chloride solution

d) Molten potassium iodide

(Answer: C)

2. A real gas deviates from ideal behaviour because the molecules in a real gas

i. have different speeds

ii. have a definite size

iii. are subject to intermolecular forces

a) 1,2, and 3 are correct

b) 1 and 2 only are correct

c) 2 and 3 only are correct

d) 1 only is correct

(Answer: C)

3) In an electrolysis experiment, the same quantity of electricity deposited 16g of copper and 54g of metal X (Ar = 108). What was the charge on the ion of metal, X?

a) +1

b) +2

c) +3

d) +4

(Answer: A)

Thanks in advance!

Uncertain SG

(1) use your data booklet, look at E potential of H, Cu, Ag, Li. Last one is confirmed out cos only K+ ion present.

Li, as compared to H, is negative E potential that means it is more preferred to exist as Li+. So H2 is liberated.

Cu and Ag, as compared to H, are positive E potential that means that are more preferred to be reduced. So Cu and Ag metal are deposited.

(2) Ideal gas assumptions are negligible intermolecular forces and negligible volume. Nothing to do with different speed.

(3) Ar = 108 can only means silver which can only have a charge of +1.

dreamthinkdo_ers SG

Hello, I have a couple of chemistry questions. Hope I can get some answers before tomorrow's exams. Please kindly explain why the answer is such.

1. Which of the following would produce bubbles of gas at each electrode, when electrolysed using platinum electrodes?

a) Copper(II) sulphate solution

b) Silver nitrate solution

c) Lithium chloride solution

d) Molten potassium iodide

(Answer: C)

a) ions present is Cu2+ , H+, OH- and SO42-

Cu2+ is discharged instead of H+ as Cu is less reactive

OH- will be discharge hence O2 produced

b) ions present is Ag+, H+, NO3- and OH-

same Ag+ is is discharged instead of H+ as Cu is less reactive

OH- will be discharge hence O2 produced

c) ions present Li+ , H+, Cl- and OH-

H+ is dicharged instead as Li is more reactive

OH- will be discharge hence O2 produced, Cl- will only be discharged is it is in high conc.

d) ion present K+ , I -

So no option, K and I2 discharged

2. A real gas deviates from ideal behaviour because the molecules in a real gas

i. have different speeds

ii. have a definite size

iii. are subject to intermolecular forces

a) 1,2, and 3 are correct

b) 1 and 2 only are correct

c) 2 and 3 only are correct

d) 1 only is correct

(Answer: C)

Ideal gas law assume that the molecules size is neglible and molecules does not interfer with each other so the IMF shd be minimise.

3) In an electrolysis experiment, the same quantity of electricity deposited 16g of copper and 54g of metal X (Ar = 108). What was the charge on the ion of metal, X?

a) +1

b) +2

c) +3

d) +4

(Answer: A)

16 g of Cu is 16/64 = 0.25 mol of Cu

we assume Cu2+ which is the most common is aq state

so 0.5 mol of electrons is involve

Since 54/108 = 0.5 mol of X is discharge

Hence charge is 1+

Thanks in advance!

1. Which of the following would produce bubbles of gas at each electrode, when electrolysed using platinum electrodes?

a) Copper(II) sulphate solution

b) Silver nitrate solution

c) Lithium chloride solution

d) Molten potassium iodide

(Answer: C)

a) ions present is Cu2+ , H+, OH- and SO42-

Cu2+ is discharged instead of H+ as Cu is less reactive

OH- will be discharge hence O2 produced

b) ions present is Ag+, H+, NO3- and OH-

same Ag+ is is discharged instead of H+ as Cu is less reactive

OH- will be discharge hence O2 produced

c) ions present Li+ , H+, Cl- and OH-

H+ is dicharged instead as Li is more reactive

OH- will be discharge hence O2 produced, Cl- will only be discharged is it is in high conc.

d) ion present K+ , I -

So no option, K and I2 discharged

2. A real gas deviates from ideal behaviour because the molecules in a real gas

i. have different speeds

ii. have a definite size

iii. are subject to intermolecular forces

a) 1,2, and 3 are correct

b) 1 and 2 only are correct

c) 2 and 3 only are correct

d) 1 only is correct

(Answer: C)

Ideal gas law assume that the molecules size is neglible and molecules does not interfer with each other so the IMF shd be minimise.

3) In an electrolysis experiment, the same quantity of electricity deposited 16g of copper and 54g of metal X (Ar = 108). What was the charge on the ion of metal, X?

a) +1

b) +2

c) +3

d) +4

(Answer: A)

16 g of Cu is 16/64 = 0.25 mol of Cu

we assume Cu2+ which is the most common is aq state

so 0.5 mol of electrons is involve

Since 54/108 = 0.5 mol of X is discharge

Hence charge is 1+

UltimaOnline SG

Very good responses from Uncertain and dreamthinkdo_ers. I've nothing further to add. This is actually how the role of a Moderator should be - moderating interactions between forum members, instead of answering all questions asked and not giving the opportunity for interaction between student peers. From now on, I won't reply to Chem questions until others have had their say, and only then I'll add my comments only if any are required or asked for. Afterall this forum is for the students, so it is for students to be the ones to discuss and interact with their peers.

Keep up the good work, and keep on Loving (Everything in Life, including Chemistry)!