HSC Chemistry Question Thread

[JaredMayo]

Hi!

Strong acids such as Hydrochloric Acid (HCl) undergo complete ionisation (all acid molecules have ionised to hydronium ions).
HCl_(g) + H₂O(l) → H₃O⁺_(aq) + Cl^-_(aq)

Weak acids such as Acetic Acid (CH₃COOH) undergo incomplete ionisation (some acid molecules have ionised to hydronium ions).
CH₃COOH_(aq) + H₂O_(l)  ⇌  H₃O⁺_(aq) + CH₃COO^-_(aq)

Here is a diagram to illustrate:
(Image removed from quote.)

Hope this helps

Edit: Added states

Hi, its 6 marks do you think i could add anything else

[nin.jas17]

Hi! I'm doing a research task on ethanol and I'm confused on the 'INDUSTRIAL production of ethanol from sugar cane.' I've done like initial research but websites keep telling me different things.

What are like the key chemical and physical process in this production?

[jakesilove]

Hi! I'm doing a research task on ethanol and I'm confused on the 'INDUSTRIAL production of ethanol from sugar cane.' I've done like initial research but websites keep telling me different things.

What are like the key chemical and physical process in this production?

Hey! Here's a brief summary of the production of ethanol from Sugar Cane.

Sugar Cane

We use sugar cane to produce ethanol because it contains biomass. Biomass makes up 50% of dry plant matter. Chemically, we are interested in the cellulose, which is a 'polymer' often made of over 10,000 glucose base units. A huge amount of biomass is produced each year; over 5*10^11 tones of the stuff! This makes biomass incredibly renewable.

First, we smash up the sugar cane to extract the biomass.

Cellulose to Glucose

Next, we want to turn the cellulose into glucose. Remember, glucose is the 'monomer' of cellulose. To do this, we either use acid electrolysis or specific enzymes which digest cellulose. You don't need to understand how either of these processes work; just that they do, and that they are expensive and time consuming.

Glucose to ethanol

Next, we want to turn our glucose into ethanol. To do this, we ferment the glucose. Successful fermentation requires a number of conditions to be met;

• pH neutral water
• Yeast
• Low oxygen concentrations
• Nutrients (eg. glucose)
• Alcohol concentrations of <14%
• Warm temperatures (around 30 degrees)

The chemical equation which describes fermentation is


 
Ethanol purification

Now, we have a mixture of ethanol, glucose, yeast, and a bunch of other stuff that we don't want. To purify the ethanol, we use a technique called fractional distillation. This exploits the difference in boiling points between different substances to extract a particular substance. Ethanol has a low boiling point (as it is an alcohol), and so readily boils!


Hope this helps!

Jake

[MisterNeo]

Hi, its 6 marks do you think i could add anything else

Acids exhibit their properties through ionisation to form the H⁺ ion (proton). However, not all acids ionise to the same extent as they can be either strong or weak in nature.
Hydrochloric acid is an example of a strong ionisation acid in water, as it is 'willing' to donate its proton to a water molecule to form H₃O⁺, and it's equation lies well to the right.

Acetic acid is an example of a weak ionisation acid in water, as it isn't 'willing' to donate its proton to water, and lies well to the left, forming an equilibrium.

As a result, HCl is more acidic than acetic acids as it has more H⁺ ions in solution.

A diagram would be helpful too. Maybe talk about bases if you have enough room.

[itssona]

Hii
stuck on this
write the half equations, overall reaction and shorthand representation for the following electrochemical cell:
an electrode consists of a piece of silver dipping into a silver nitrate solution. Its connected by a salt bridge to another electrode consisting of a piece of platinum dipping into a chloride solution with chlorine gas bubbling through the solution over the inert platinum electrode. The platinum is the positive electrode

so
not sure, because they are dipped in different solutions
am I right by saying that platinum is the cathode and thus is "reducing"
how does this cell work?

[MisterNeo]

Hii
stuck on this
write the half equations, overall reaction and shorthand representation for the following electrochemical cell:
an electrode consists of a piece of silver dipping into a silver nitrate solution. Its connected by a salt bridge to another electrode consisting of a piece of platinum dipping into a chloride solution with chlorine gas bubbling through the solution over the inert platinum electrode. The platinum is the positive electrode

so
not sure, because they are dipped in different solutions
am I right by saying that platinum is the cathode and thus is "reducing"
how does this cell work?

Hey
It would be correct to say that platinum 'acts as a cathode', however it's not reducing itself but the chlorine gas (watch out for wording). The cell works like any other galvanic cell where there are two half-cells. This one uses a platinum electrode because chlorine gas can't have a solid chlorine electrode, hence it's bubbled through.
Since the chlorine is going to be reduced (positive cathode), its half equation would be:

The silver would be the anode and is being oxidised:

Overall:

Hope this helps

[justwannawish]

Hey guys,

How do you do questions when you're finding the [H+] concentration and how does that vary with finding the concentration of a solution itself? Do you have to consider diprotic acids for both or just for the H+ concentration

[RustyWasTaken]

 Hello please help me"Outline the chemistry of the fermentation process and using flow charts, compare the process of the industrial production of ethanol from both sugarcane and petroleum. Label and state the purpose of each step in the process. (5 MARKS). Not sure how to answer properly

[Natasha.97]

Hello please help me"Outline the chemistry of the fermentation process and using flow charts, compare the process of the industrial production of ethanol from both sugarcane and petroleum. Label and state the purpose of each step in the process. (5 MARKS). Not sure how to answer properly

Hi!

For petroleum, you would have the following steps:
- Fractional distillation: Separates crude oil into its constituent fractions
- Thermal cracking of long-chained hydrocarbons (750°C) OR catalytic cracking (Zeolite, 500°C) to form ethylene
- Catalytic hydration of ethylene (H₂SO₄/H₃PO₄) into ethanol

For sugarcane (cellulose), you would have the following steps
-Enzymatic breakdown by zymase/maltase/invertase to form glucose
-Fermentation of glucose to form ethanol: List out essential conditions such as an anaerobic environment, water (for the reaction to take place in), alcohol tolerant yeast (maximum is 15%), and a moderately warm temperature (~30°C).
-Distillation: The ethanol produced is at 15%. Fractional distillation can be used to produce concentrated ethanol (~96%)

Hope this helps

[Aaron12038488]

help. Describe how transuranic isotopes are produced in particle accelerators?
 use an equation to support this

[MisterNeo]

help. Describe how transuranic isotopes are produced in particle accelerators?
 use an equation to support this

Hey
Firstly, I would state that particle accelerators can linear or cyclotrons and are used to create transuranic elements such as Hassium-264 by bombarding Lead-208 with Iron-58 at high speeds achieved using electromagnetic fields.

²⁰⁸₈₂Pb + ⁵⁸₂₆Fe → ²⁶⁴₁₀₈Hs + ¹₁p

[Dragomistress]

How do I do this. Draw the polymer for ethylene.

[MisterNeo]

How do I do this. Draw the polymer for ethylene.

Hey
Ethylene can act as a monomer (repeating unit) and polymerise into polyethylene. There are two types of polyethylene, low-density and high-density. For most drawing questions, you would draw the high-density version with at least 3 monomers polymerised (you can lose marks for this). And make sure you put "[  ]" square brackets at the end of the polymer to show that it continues.

Hope this helps

[ilovemycat]

hey! anyone know how to do this heat of combustion question? im stuck

[MisterNeo]

hey! anyone know how to do this heat of combustion question? im stuck