Predictions for Chemistry 2014 HSC? (8 Viewers)

[SuchSmallHands]

Thanks. So that's enough ifo we need to know about him right? We can bs the rest?

Sometimes you'll see it written as Haber-Bosch process, knowing who Bosch is just kind of stops you freaking out and thinking they're talking about a different process (like some people did in my school's trial when they referred to it as that)

 

[enigma_1]

Sometimes you'll see it written as Haber-Bosch process, knowing who Bosch is just kind of stops you freaking out and thinking they're talking about a different process (like some people did in my school's trial when they referred to it as that)

Ooh ok thanks!

 

[SuchSmallHands]

Ooh ok thanks!

No worries

New question: outline two methods of depolymerising cellulose to glucose (4 marks)

 

[GOsie]

No worries

New question: outline two methods of depolymerising cellulose to glucose (4 marks)

Is that even in the syllabus?

 

[SuchSmallHands]

Is that even in the syllabus?

I think it comes under cellulose as a raw material. We depolymerise, ferment and then either just collect the ethanol or dehydrate to ethene.

 

[Hi there444]

I think it comes under cellulose as a raw material. We depolymerise, ferment and then either just collect the ethanol or dehydrate to ethene.

Hydrolyse

_/_/_

 

[GOsie]

No questions? I'll get the ball rolling again.

Describe both a quantitative and a qualitative test for either hardness or turbidity of water (4 marks)

 

[SuchSmallHands]

No questions? I'll get the ball rolling again.

Describe both a quantitative and a qualitative test for either hardness or turbidity of water (4 marks)

Yeah I don't think anyone's going to answer mine.
Hardness
Quantitative: The water sample is delivered through a burette into a conical flask containing erio-t indicator and EDTA of a known quantity and molarity. When the indicator changes colour, it indicates that all of the EDTA is complexed with Ca2+ or Mg2+ ions, and as such the erio-t indicator is uncomplexed and changes colour from pink to blue. Concentration of Ca2+ and Mg2+ in the sample, and thus hardness, can be determined by calculating the volume of the water sample required to cause all of the EDTA4- ions to form chelates with the Ca2+ and Mg2+ in the sample.
Qualitative: Attempt to lather soap in the water. Inability to build up a lather indicates hard water.

 

[SuchSmallHands]

Outline the procedure you used to distinguish between an alkene and the corresponding alkane (3 marks)

 

[SuchSmallHands]

No questions? I'll get the ball rolling again.

Describe both a quantitative and a qualitative test for either hardness or turbidity of water (4 marks)

Just out of curiosity, I really don't know what a qualitative test for turbidity is. Do you just look at the water and say 'yep, that looks pretty murky' or is there a proper test? (good question, I hadn't even realised I didn't know that)

 

[QZP]

Just out of curiosity, I really don't know what a qualitative test for turbidity is. Do you just look at the water and say 'yep, that looks pretty murky' or is there a proper test? (good question, I hadn't even realised I didn't know that)

I thought turbidity tube / secchi disc was a qualitative test

 

[GOsie]

Outline the procedure you used to distinguish between an alkene and the corresponding alkane (3 marks)

In a darkened lab (absence of UV light), a test tube is filled with 5ml of cyclohexane and a second test tube is filled with 5ml of cyclohexene.

3 drops of (brown) bromine water is added to each tube. A stopper is placed on top, and the test tubes are both shaken.

The test tube containing cyclohexane will remain a brownish colour, due to no reaction taking place. The test tube containing cyclohexene will go from brownish to colourless.

C6H10 (L) + Br2 (L) --> C6H10Br2 (L)

The double bond within cyclohexene is broken, thus both bromine atoms may combine to the carbons atoms that shared the C=C double bond.

 

[SuchSmallHands]

I thought turbidity tube / secchi disc was a qualitative test

Turbidity tube is quantitative, you get a result in NTUs. I never used a secchi disk, what does that give the result in? Is it just yes/no?

 

[SuchSmallHands]

In a darkened lab (absence of UV light), a test tube is filled with 5ml of cyclohexane and a second test tube is filled with 5ml of cyclohexene.

3 drops of (brown) bromine water is added to each tube. A stopper is placed on top, and the test tubes are both shaken.

The test tube containing cyclohexane will remain a brownish colour, due to no reaction taking place. The test tube containing cyclohexene will go from brownish to colourless.

C6H10 (L) + Br2 (L) --> C6H10Br2 (L)

The double bond within cyclohexene is broken, thus both bromine atoms may combine to the carbons atoms that shared the C=C double bond.

We use bromine water (ie. aqueous bromine) in this prac, but other than that definitely 3/3

 

[GOsie]

Just out of curiosity, I really don't know what a qualitative test for turbidity is. Do you just look at the water and say 'yep, that looks pretty murky' or is there a proper test? (good question, I hadn't even realised I didn't know that)

As QZP said, the Secchi disc is a qualitative test. A quantitative test would be (I think - could someone please confirm), evaporating the water and weighing the solid remains.

 

[enigma_1]

Turbidity tube is quantitative, you get a result in NTUs. I never used a secchi disk, what does that give the result in? Is it just yes/no?

Secchi disk looks like this http://friendsofgulfstvincent.org.au/wp-content/uploads/2012/10/Secchi-disk.jpg

You pretty much lower the disk until the 4 quadrants are no longer visible/distinguishable and then you measure the length of the rope required to achieve this and hence turbidity is determined quantitatively

 

[QZP]

Turbidity tube is quantitative, you get a result in NTUs. I never used a secchi disk, what does that give the result in? Is it just yes/no?

In that case I believe secchi disc is a qualitative test since it only gives relative turbidity (distance of string)

 

[GOsie]

We use bromine water (ie. aqueous bromine) in this prac, but other than that definitely 3/3

So all I need to do is change mine to Br2 (aq) ?

or is it a different molecule?

 

[enigma_1]

I thought turbidity tube / secchi disc was a qualitative test

As QZP said, the Secchi disc is a qualitative test. A quantitative test would be (I think - could someone please confirm), evaporating the water and weighing the solid remains.

guys no it's actually a quantitative test, please see the above explanation.
I can understand why it would be deemed as qualitative however realistically the only qualitative test is if the water looks brown or murky. But secchi disk is quantitative

 

[enigma_1]

In that case I believe secchi disc is a qualitative test since it only gives relative turbidity (distance of string)

guys no it's actually a quantitative test, please see the above explanation.
I can understand why it would be deemed as qualitative however realistically the only qualitative test is if the water looks brown or murky. But secchi disk is quantitative

^

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