VCE Chemistry Question Thread

[daniel.h]

2013 VCAA Exam 2 Q25 MCQ: no reaction is observed and that's because of the slow reaction rate

2011 VCAA Exam 2 Q4a) short answer: reaction does not occur to any significant extent and this is because the strongest reductant and oxidant need to react

but doesn't "reaction does not occur to any significant extent" (mean that the reaction still happens but not to a significant extent, so slow rate would be the reason?

And how are those 2 questions different

bump

[daniel.h]

do we need to know how to do vcaa 2008 exam 1 mcq q 20
like fractional distillation stuff

and is vcaa 2008 exam 1 short ans q2b) still in tje course

[LaurenRoth18]

When doing titration questions that involves finding the concentration of h2so4 is it required to divide whatever answer you get by 2 as there are 2 h+ ions? Thanks.

[Spooky]

For water, the data book gives the density as 0.997 g/ml.
Does this mean if we are given 100g of water we should calculate it as 99.7 ml, like for calculating heat energy released?

[Lear]

No, when using the MCAT formula we use the mass of water no the volume. If mass is given you just use that directly but if the volume is given you must convert to grams using the density.

[Bri MT]

When doing titration questions that involves finding the concentration of h2so4 is it required to divide whatever answer you get by 2 as there are 2 h+ ions? Thanks.

Your working for a titration q should be something like this:
1. Find the number of mols of the thing you know the conc. of already (the titrant)
2. Use the molar ratio and n(titrant) to find n(analyte)    (the analyte is the thing you don't know the concentration of)
If they have the same number of mols, make sure you write that (eg. n(titrant)=n(analyte) )

This is where you would do a division by 2 if two hydrogens are donated, but keep in mind that it's usually significantly easier for an acid to give up its first H+ than its 2nd one, so even though H2SO4 can give up two protons, if you're not titrating with a basic titrant I would assume it just gives up one.

3. use n=cv and the fact that you now know n(analyte) to find c(analyte)
4. If needed, use c1v1=c2v2 to account for dilutions
5. Report your answer using correct sig figs and units


Hope this helps

[Azim.m]

do we need to know how to do vcaa 2008 exam 1 mcq q 20
like fractional distillation stuff

and is vcaa 2008 exam 1 short ans q2b) still in tje course

Q20) not too sure, but you can still answer it with the knowledge from the current chemistry study design, such as volatility and boiling points.

Q2b) No, UV-visible spectroscopy is out of the chem course

[ezferns]

Hey everyone, I've got a couple of questions.

1. Do we need to know the relationship between a specific voltage and the products of an electrolysis reaction? Like would we need to derive the voltage of an electrolytic cell given its reactions?

2. How many significant figures do we use if we're given data like 'one hour'? What if we get '30 minutes'? Do we use 1 sig fig?

3. When is chloride oxidised in preference to water? What kind of context in the stimulus should I look out for?

4. What states do we use for products in a galvanic cell which uses a paste electrolyte? aq or s?

Thanks in advance!!

[Maths Forever]

Q20) not too sure, but you can still answer it with the knowledge from the current chemistry study design, such as volatility and boiling points.

Q2b) No, UV-visible spectroscopy is out of the chem course

Fractional distillation used to be part of the study design before 2013. However, as far as I know, it is no longer explicitly part of the study design.

[Maya24]

In the electrochemical series, there are several H20. Which equation would I need to pick?

[passbleh24]

In the electrochemical series, there are several H20. Which equation would I need to pick?

Depends on what the conditions are:
Whether there is oxygen present or not alongside H20.
If mixture is acidic or basic will determine if H+ is present of OH-

Choosing between the relevant equations will depend on which equations contain the strongest reductant and oxidant.

[rinner]

Hey guys,
I can't seem to figure out how to work out the answer to this question, can anyone help?
29) A helium cylinder for the inflation of party balloons holds 25.0 L of gas, and is filled to a pressure of 16 500 kPa at 15°C
d) How many balloons can be inflated from a single cylinder at 30°C if the volume of one balloon is 6.5 L and each needs to be inflated to a pressure of 108 kPa?
ANS- 618
thanks in advance !!!

[Bri MT]

Hey guys,
I can't seem to figure out how to work out the answer to this question, can anyone help?
29) A helium cylinder for the inflation of party balloons holds 25.0 L of gas, and is filled to a pressure of 16 500 kPa at 15°C
d) How many balloons can be inflated from a single cylinder at 30°C if the volume of one balloon is 6.5 L and each needs to be inflated to a pressure of 108 kPa?
ANS- 618
thanks in advance !!!

If you get really lost on a chem question,  see if you can calculate the number of mols

Let me know if you need further help

[Azzzz]

Hey guys,
I can't seem to figure out how to work out the answer to this question, can anyone help?
29) A helium cylinder for the inflation of party balloons holds 25.0 L of gas, and is filled to a pressure of 16 500 kPa at 15°C
d) How many balloons can be inflated from a single cylinder at 30°C if the volume of one balloon is 6.5 L and each needs to be inflated to a pressure of 108 kPa?
ANS- 618
thanks in advance !!!

Okay, so how I would approach this question is first to identify what values I am able to use and identify what formula I must utilise in order to use all those values.
Since we are given the temp, volume and pressure, we would use the PV=nRT and rearrange for n.
So (PV)/(RT)=n
Input the values
(16,500 x 25)/(8.314 x 288) which is 172.2746773 mol for the helium cylinder.
Do the same thing for a singular balloon.
(108 x 6.5)/(8.314 x 303) which is .2786663078 mol.
So to find how many balloons can be inflated from the helium cylinder we would divide the total mol within the helium cylinder by the mol required by the balloons so 172.2746773/.2786663078 = 618
I used all the decimal places in order to get the most precise answer.
If anyone can improve upon my answer please do so

[Azim.m]

Hey guys,
I can't seem to figure out how to work out the answer to this question, can anyone help?
29) A helium cylinder for the inflation of party balloons holds 25.0 L of gas, and is filled to a pressure of 16 500 kPa at 15°C
d) How many balloons can be inflated from a single cylinder at 30°C if the volume of one balloon is 6.5 L and each needs to be inflated to a pressure of 108 kPa?
ANS- 618
thanks in advance !!!

Hint: use the formula PV = nRT , rearrange to find n(helium)