VCE Chemistry Question Thread

[deStudent]

http://m.imgur.com/AtWxSGb

How isn't B, also correct? A decreased SA, means less particles will react, hence a slower reaction rate?

Ty

[sweetiepi]

http://m.imgur.com/AtWxSGb

How isn't B, also correct? A decreased SA, means less particles will react, hence a slower reaction rate?

Ty

From what I see, B talks about making smaller pieces of zinc, which increases surface area. More surface area means that more particles can react, therefore a higher reaction rate.

(Hope this helps )
(Correct me if I'm wrong, I'm a tad rusty on reaction rates )

[deStudent]

From what I see, B talks about making smaller pieces of zinc, which increases surface area. More surface area means that more particles can react, therefore a higher reaction rate.

(Hope this helps )
(Correct me if I'm wrong, I'm a tad rusty on reaction rates )

Yeah, I think that's correct. I was just about to delete this question after re-reading it lmao.

Thanks for the help anyway.

[peanut]

Is this definition for activation energy sufficient?

Activation energy is the minimum energy required to break the bonds in the reactants and to form the bonds in the products for the reaction to proceed.

[Syndicate]

Is this definition for activation energy sufficient?

Activation energy is the minimum energy required to break the bonds in the reactants and to form the bonds in the products for the reaction to proceed.

Should be fine

[lzxnl]

Is this definition for activation energy sufficient?

Activation energy is the minimum energy required to break the bonds in the reactants and to form the bonds in the products for the reaction to proceed.

Activation energy has nothing to do with bond formation. It's JUST the minimum energy needed to break bonds.

[zhen]

Can someone please help me with this question. When 1.0 g of ethene undergoes complete combustion, what mass of water vapour is produced? I keep on getting 1.3 g, but the answer says 3.6 g. What am I doing wrong?

[zhen]

Could someone also help me with this question. What is the final sulfate ion concentration after mixing 100 cm3 of 0.4 M. Al2(SO4)3 and 150 cm3 of 0.2 M Ba(NO3)2?  Apparently the answer is 0.48M, but how can the concentration increase when I'm mixing two different things together?

[Syndicate]

Could someone also help me with this question. What is the final sulfate ion concentration after mixing 100 cm3 of 0.4 M. Al2(SO4)3 and 150 cm3 of 0.2 M Ba(NO3)2?  Apparently the answer is 0.48M, but how can the concentration increase when I'm mixing two different things together?

The concentration of SO4 in Al2(SO4)3 is 3 x 0.4 = 1.2 M

Al2(SO4)3 percentage in the mixed solution = 100/250 x 100% = 40%

SO4 concentration = 0.4 x 1.2 = 0.48 M

I did this kind of question more than a year ago, it would be great if someone can confirm if me working out is valid.

[Shadowxo]

The concentration of SO4 in Al2(SO4)3 is 3 x 0.4 = 1.2 M

Al2(SO4)3 percentage in the mixed solution = 100/250 x 100% = 40%

SO4 concentration = 0.4 x 1.2 = 0.48 M

I did this kind of question more than a year ago, it would be great if someone can confirm if me working out is valid.

Working out is right, but I'd go the n(So4) and final volume route to find concentration, c=n/v, though that is a useful shortcut.

[deStudent]

I answered C, but the book wrote D only. Isn't C implying that the rate of the collisions is increased since more collisions can occur between reactants?
http://m.imgur.com/q9z7HUk

(Answer D is worded pretty dodgy tho)

[sweetiepi]

I answered C, but the book wrote D only. Isn't C implying that the rate of the collisions is increased since more collisions can occur between reactants?
http://m.imgur.com/q9z7HUk

(Answer D is worded pretty dodgy tho)

Imo the book only says d, as there is the key word frequency.
C is correct, however D is deemed to be "more" correct.

(Sorry for my scarce response- I'm out and on my phone, avoiding playing musical chairs, haha)

[Shadowxo]

I answered C, but the book wrote D only. Isn't C implying that the rate of the collisions is increased since more collisions can occur between reactants?
http://m.imgur.com/q9z7HUk

(Answer D is worded pretty dodgy tho)

Often in multiple choice they try to "trick" you, especially like this.
C just says number of collisions, and overall there are the same number of collisions in both scenarios - same number of reactions overall, which is why it's "wrong" even though it implies more collisions in a given period of time.
D could have been worded better - the "than" shouldn't be there. But they want you to notice the concentration increases the rate of reaction due to the increased frequency of collisions. It should have been worded better though

[zhen]

The concentration of SO4 in Al2(SO4)3 is 3 x 0.4 = 1.2 M

Al2(SO4)3 percentage in the mixed solution = 100/250 x 100% = 40%

SO4 concentration = 0.4 x 1.2 = 0.48 M

I did this kind of question more than a year ago, it would be great if someone can confirm if me working out is valid.

Thanks. Do you know how to do this question? When 1.0 g of ethene undergoes complete combustion, what mass of water vapour is produced? I keep on getting 1.3 g, but the answer says 3.6 g. What am I doing wrong?

[Syndicate]

Can someone please help me with this question. When 1.0 g of ethene undergoes complete combustion, what mass of water vapour is produced? I keep on getting 1.3 g, but the answer says 3.6 g. What am I doing wrong?

I think your answer is correct, because H2O has a 2:1 ratio with C2H4.

n(C2H4) = 1/28 mol

n(H2O) = 1/14

m(H2O) = 9/7 = ~1.29 grams