Predictions for Chemistry 2014 HSC? (9 Viewers)

[photastic]

Lol yeah maybe. But then what was the point of all whole Q No calculations? Let's just say dodgy Q

Alright, it's an illuminati question. Please replace with the most common questions of all time below.

Explain why carbonated drinks are better consumed when cold, in terms of the effect on the drink’s acidity. Include a relevant chemical equation in your answer. (3 marks)

A bottled carbonated drink was decarbonated and found to have a final mass of 350.61 g. The volume of gas released at 25°C and 100 kPa was determined to be 1.86 L. Calculate the original mass of the bottled carbonated drink. (2 marks)

 

[faisalabdul16]

Alright, it's an illuminati question. Please replace with the most common questions of all time below.

Explain why carbonated drinks are better consumed when cold, in terms of the effect on the drink’s acidity. Include a relevant chemical equation in your answer. (3 marks)

A bottled carbonated drink was decarbonated and found to have a final mass of 350.61 g. The volume of gas released at 25°C and 100 kPa was determined to be 1.86 L. Calculate the original mass of the bottled carbonated drink. (2 marks)

The whole point and importance of adding acid to drinks is to give them a tangy taste. If no acid is present then one would be consuming coloured water with sugar.
CO2(g) + H2O(l) (equilibrium sign) H2CO3(aq) (equilibrium sign) H(+) + HCO3(-) + heat
These drinks are better consumed cold as it causes equilibrium to shift to the right, resulting in more of the products, and in the process carbon dioxide is used (dissolved in the drink). According to LCP, if you decrease temperature (cooling) equilibrium will shift to the right to counteract that change, and as a result the solubility of carbon dioxide increases and provides a greater tangy taste. Hence why carbonated drinks are better consumed cold.

1 mark - equation
1 mark - LCP explanation
1 mark - what happens to solubility of Carbon dioxide and why it's added.


Answer to calculation question, 353.91g

 

[faisalabdul16]

I thought the question below was really nice and neat.

A student titrated 0.14 M barium hydroxide solution with 22.35mLs of 0.08M nitric acid.
(a) Write a balanced chemical equation for this reaction. 1 mark
(b) Calculate the volume of barium hydroxide required in this titration. 2 marks
(c) The student accidentally spilt an excess 13.5mL of barium hydroxide into the mixture. Calculate the pH of the resulting solution. 4 marks

 

[photastic]

The whole point and importance of adding acid to drinks is to give them a tangy taste. If no acid is present then one would be consuming coloured water with sugar.
CO2(g) + H2O(l) (equilibrium sign) H2CO3(aq) (equilibrium sign) H(+) + HCO3(-) + heat
These drinks are better consumed cold as it causes equilibrium to shift to the right, resulting in more of the products, and in the process carbon dioxide is used (dissolved in the drink). According to LCP, if you decrease temperature (cooling) equilibrium will shift to the right to counteract that change, and as a result the solubility of carbon dioxide increases and provides a greater tangy taste. Hence why carbonated drinks are better consumed cold.

1 mark - equation
1 mark - LCP explanation
1 mark - what happens to solubility of Carbon dioxide and why it's added.


Answer to calculation question, 353.91g

 

[faisalabdul16]

Have a go at the calculation question i posted.

 

[SuchSmallHands]

I did some stalking and I don't think SSH goes to baulko.

No I don't haha, it's just the only school I know of that does it. Sydney Grammar did it ten years ago, because I have some of their trials from like 2003-5 for study, but isn't know if they still do.

 

[QZP]

Have a go at the calculation question i posted.

Just some Q's, are all our final answers meant to be in 1 sig fig? Also, for last part am I allowed to assume that the equivalent point of a strong acid + strong base titration has a pH of 7? (i.e. initial pH of mixture = 7)

 

[faisalabdul16]

Just some Q's, are all our final answers meant to be in 1 sig fig? Also, for last part am I allowed to assume that the equivalent point of a strong acid + strong base titration has a pH of 7? (i.e. initial pH of mixture = 7)

Don't worry about sig fig, just write your answers.

bold part - are you sure? Plus it's pH of final mixture you are finding

 

[QZP]

Don't worry about sig fig, just write your answers.

bold part - are you sure? Plus it's pH of final mixture you are finding

In HSC, how many sig figs do they want?

And yes, is that wrong? After titration (which is 1st part), then pH of mixture = 7. So then I just need to calculate how many OH ions from the spillage of Ba(OH)2 from which I can then determine the pOH and thus pH

 

[Queenroot]

For chemistry 4 sig figs is standard, but in HSC it's fucked and you should do it according to the other values in the question.

 

[faisalabdul16]

In HSC, how many sig figs do they want?

And yes, is that wrong? After titration (which is 1st part), then pH of mixture = 7. So then I just need to calculate how many OH ions from the spillage of Ba(OH)2 from which I can then determine the pOH and thus pH

In HSC, the number of sig figs they want is the number of sig figs they give you.

For instance, if a question says blah blah blah 4.567 bdhfgashdfahdfshfds, then your answer should be 4 sig figs.

If it says ssgfsdfgdfg 0.345 mol then your answer should be 3 sig figs such as 0.123

Also, I'm not sure as to what you're doing for the calculation question, so tell me your final answers.

 

[QZP]

So in this question its 1 sig fig right? Okay hold on let me do it

 

[faisalabdul16]

Also guys, this is 2012 BOS chemistry trials. This is actually a really nice paper, thanks to "someth1ng" and "addoil"


View attachment BOS Chemistry Trial Paper 2012.pdf
View attachment BOS Chemistry Trial Paper 2012 Marking Guidelines.pdf

 

[QZP]

Okay I got their answer that's good

 

[QZP]

Just to clarify what I was saying before about assuming initial pH = 7, suppose the question was changed from Ba(OH)2 + HNO3 to Ba(OH)2 + CH3COOH. The equivalent point of strong base + weak acid would not be 7 but on the basic side which makes the calculation a lot more complex

Edit: Nvm I probably don't make sense

 

[faisalabdul16]

Just to clarify what I was saying before about assuming initial pH = 7, suppose the question was changed from Ba(OH)2 + HNO3 to Ba(OH)2 + CH3COOH. The equivalent point of strong base + weak acid would not be 7 but on the basic side which makes the calculation a lot more complex

Edit: Nvm I probably don't make sense

With calculations you never know what the pH is going to be like because it may be a limiting reagent question.
For instance if you have 1mL of Sodium hydroxide and 5000L of HCl, the resultant solution will have a pH < 7 because it's a limiting reagent question, with sodium hydroxide being the limiting reagent.

 

[QZP]

Also guys, this is 2012 BOS chemistry trials. This is actually a really nice paper, thanks to "someth1ng" and "addoil"


View attachment 30984
View attachment 30985

Is there a 2013 one? o_o or other years

 

[iStudent]

In HSC, the number of sig figs they want is the number of sig figs they give you.

For instance, if a question says blah blah blah 4.567 bdhfgashdfahdfshfds, then your answer should be 4 sig figs.

If it says ssgfsdfgdfg 0.345 mol then your answer should be 3 sig figs such as 0.123

Also, I'm not sure as to what you're doing for the calculation question, so tell me your final answers.

Then there are those questions with e.g. ..."three flasks with 25 ml of water and 10 ml of ethanol " and you're supposed to ignore these :/
take a look at hsc 2012 q30bi

 

[faisalabdul16]

Is there a 2013 one? o_o or other years

I'm not sure... I know there is a 2014 one, however the creator of the paper has not uploaded it yet.

New question
A radioisotope undergoes 2 alpha decays, followed by a beta decay, forming actinium-230 as a result. What was the original radioisotope?

 

[MrBeefJerky]

I'm not sure... I know there is a 2014 one, however the creator of the paper has not uploaded it yet.

New question
A radioisotope undergoes 2 alpha decays, followed by a beta decay, forming actinium-230 as a result. What was the original radioisotope?

Is it U-238