VCE Chemistry Question Thread

[daniel.h]

Hey everyone,

In the image to the right (the mirror image), can we also write H3CH2C, HO and NC since it's the mirror image? If it doesn't matter how we write it, is the only important thing that the central carbon is bonded to the right atom e.g. central carbon is bonded to C in CH2CH3, not H

[MAGGOT]

Do we need to know the qualitative  tests of alcohols?

[IonianDeo]

Confusion between Option A and B.

[Bri MT]

Confusion between Option A and B.

The key here is that line 2 is lower than line 1, meaning that more magnesium TOTAL has reacted.

Magnesium is in excess, so n(HCL) is limiting & n=cv

[sweetcheeks]

Hey everyone,

In the image to the right (the mirror image), can we also write H3CH2C, HO and NC since it's the mirror image? If it doesn't matter how we write it, is the only important thing that the central carbon is bonded to the right atom e.g. central carbon is bonded to C in CH2CH3, not H

Perfectly fine as long as you are correctly showing the bonding

Do we need to know the qualitative  tests of alcohols?

From the study design
organic reactions, including appropriate equations and reagents, for the oxidation of primary and secondary
alcohols, substitution reactions of haloalkanes, addition reactions of alkenes, hydrolysis reactions of esters, the
condensation reaction between an amine and a carboxylic acid, and the esterification reaction between an
alcohol and a carboxylic acid.

It appears that you need to have some level of understanding of the oxidation reactions. I would say that it likely that you just need to know that adding permanganate or dichromate to a primary alcohol yields an aldehyde which can be oxidised further into a carboxylic acid. A secondary alcohol is oxidised to a ketone.

[MM123]

Could someone help me out with question 4?

[Vaike]

Could someone help me out with question 4?

Hey! This one is a bit tricky. It's essentially asking you to justify why HOBr(aq) would not be produced. Have a look at the reaction involving bromine ions in the data booklet, and compare it against the equation given. What do you notice about their standard electrode potentials?

[Guideme]

Can anyone explain why it is 1 Chloropentan-4-ol and not 5Chloropentan-2-ol

[MAGGOT]

Can anyone explain why it is 1 Chloropentan-4-ol and not 5Chloropentan-2-ol

Shouldn't it be 5-chloropentan-2-ol?

[Seno72]

 

Can anyone explain why it is 1 Chloropentan-4-ol and not 5Chloropentan-2-ol

Remember that you have to name by first looking for the longest carbon chain. That's pretty easy and so it's pentane. Then we have to number the carbon chains based on the functional groups we have in the chain. We have a halogen functioning group (Cl) and a alcohol group (OH). Due to IUPAC rules, the alcohol group (OH) has a higher priority than the chlorine and so we start numbering the carbon atoms from the end of the chain closest to the alcohol group. The alcohol is in the second carbon (starting from the left) and the chlorine is in the fifth carbon. Since alcohol has the highest priority, we have to have it as a suffix (~ol) at the end. Chlorine is written at the front in this case as 'chloro'.(Most of the time you write prefixes for halogens) Therefore it would be 5-chloropentan-2-ol. Hope that helps.

[Meddling]

Hey guys just a quick question:

During the dissolution of polar solutes in water, do the water molecules form dipole-dipole bonds with the polar solute molecules?

Thanks!

Yeah, polar solvents dissolve polar solutes; hydrogen bonding, and whether they form electrolyte or not depends on the type of molecule

[Seno72]

Hey guys. My Chemistry grade is in a bit of a dilemma. I thought we were going to do Organic Chemistry first but we are doing Food Chemistry (the sac) before Organic Chemistry. Do I need to know a lot from Organic Chemistry to do Food Chemistry?

[sweetiepi]

Hey guys. My Chemistry grade is in a bit of a dilemma. I thought we were going to do Organic Chemistry first but we are doing Food Chemistry (the sac) before Organic Chemistry. Do I need to know a lot from Organic Chemistry to do Food Chemistry?

According to the VCAA:

Key knowledge
Key food molecules
• proteins: formation of dipeptides and polypeptides as condensation polymers of 2-amino acids; primary (including peptide links), secondary, tertiary and quaternary structure and bonding; distinction between essential and non-essential amino acids as dietary components
• carbohydrates: formation of disaccharides from monosaccharides, and of complex carbohydrates (specifically starch and cellulose) as condensation polymers of monosaccharides; glycosidic links; storage of excess
glucose in the body as glycogen; comparison of glucose, fructose, sucrose and the artificial sweetener
aspartame with reference to their structures and energy content
•fats and oils (triglycerides): common structural features including ester links; distinction between fats and oils with reference to melting points; explanation of different melting points of triglycerides with reference to the structures of their fatty acid tails and the strength of intermolecular forces; chemical structures of saturated and unsaturated (monounsaturated and polyunsaturated) fatty acids; distinction between essential and nonessential fatty acids; and structural differences between omega-3 fatty acids and omega-6 fatty acids
•vitamins: inability of humans to synthesise most vitamins (except Vitamin D) making them essential dietary requirements; comparison of structural features of Vitamin C (illustrative of a water-soluble vitamin) and Vitamin D (illustrative of a fat-soluble vitamin) that determine their solubility in water or oil.

Metabolism of food in the human body
•metabolism of food as a source of energy and raw materials: general principles of metabolism of food involving enzyme-catalysed chemical reactions with reference to the breakdown of large biomolecules in food by hydrolytic reactions to produce smaller molecules, and the subsequent synthesis of large biologically important
molecules by condensation reactions of smaller molecules
• enzymes as protein catalysts: active site; modelling of process by which enzymes control specific biochemical reactions (lock-and-key and induced fit models); consequences of variation in enzyme-substrate interaction (lock-and-key mechanism) due to the behaviour of a particular optical isomer; explanation of effects of changes in pH (formation of zwitterions and denaturation), increased temperature (denaturation) and decreased temperature (reduction in activity) on enzyme activity with reference to structure and bonding; action of enzymes in narrow pH ranges; and use of reaction rates to measure enzyme activity
•the distinction between denaturation of a protein and hydrolysis of its primary structure
•hydrolysis of starch in the body: explanation of the ability of all humans to hydrolyse starch but not cellulose, and of differential ability in humans to hydrolyse lactose; glycaemic index (GI) of foods as a ranking of carbohydrates based on the hydrolysis of starches (varying proportions of amylose and amylopectin) to produce glucose in the body
•hydrolysis of fats and oils from foods to produce glycerol and fatty acids; oxidative rancidity with reference to
chemical reactions and processes, and the role of antioxidants in slowing rate of oxidative rancidity
• the principles of the action of coenzymes (often derived from vitamins) as organic molecules that bind to the active site of an enzyme during catalysis, thereby changing the surface shape and hence the binding properties of the active site to enable function as intermediate carriers of electrons and/or groups of atoms (no specific
cases required).

From a quick read of the study design, I see concepts mentioned in this particular AOS that I have been taught throughout organic chemistry in both VCE and uni, so I'd assume some organic chemistry knowledge is needed.

[Tanya1234588]

Hello, I was wondering whether anyone had a question that incorporates majority of the electrolysis theory/ dot point in one question? Thank you (it can have an a,b,c.. etc)

[IonianDeo]

Numbering carbon chain issue/how would you name this compound?
Which functional group is of higher priority, methyl or Cl?