Prelim Chem Thread (1 Viewer)

[ThreeSciences]

Great links here but how r u going to answer it in the form of an extended response?

Those first two questions are nothing more than identify/list and the third is an explain. They're nowhere near extended response.

 

[eyeseeyou]

Those first two questions are nothing more than identify/list and the third is an explain. They're nowhere near extended response.

okay...

 

[Snowflek]

Can someone help me and explain in details cause ive been explained by people so many times but im still confused.
A sample of fertilise contains 32.5g ammonium sulfate. What is the mass of nitrogen in this fertiliser?
So i found the mole of ammonium sulfate which is 0.2421417437
then this part is where im confused. People say times 0.2421417437 by 2.
So it requires 2 ammonium to 1 sulfate where people say times by 2. But what i dont understand is that wasnt the (NH4)2 already calculated from the beginning? From by multiplying it by 2 sounds like were getting double the mole of ammonium sulfate

 

[ThreeSciences]

Can someone help me and explain in details cause ive been explained by people so many times but im still confused.
A sample of fertilise contains 32.5g ammonium sulfate. What is the mass of nitrogen in this fertiliser?
So i found the mole of ammonium sulfate which is 0.2421417437
then this part is where im confused. People say times 0.2421417437 by 2.
So it requires 2 ammonium to 1 sulfate where people say times by 2. But what i dont understand is that wasnt the (NH4)2 already calculated from the beginning? From by multiplying it by 2 sounds like were getting double the mole of ammonium sulfate

 

[eyeseeyou]

Someone please to me oxidation and reduction. I know OILRIG but I need specific examples with detailed explanation

Thanks

 

[Sien]

Someone please to me oxidation and reduction. I know OILRIG but I need specific examples with detailed explanation

Thanks

Look at the back of your periodic table


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[turntaker]

Look at the back of your periodic table


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Nice jap [emoji14]

 

[eyeseeyou]

Look at the back of your periodic table


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I need examples and detailed explanation

Also need help with half equations and spectator ions

 

[turntaker]

I need examples and detailed explanation

Also need help with half equations and spectator ions

Inbox him for more help

 

[Sien]

Inbox him for more help

I don't do chem

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[eyeseeyou]

I don't do chem

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Yes you do

 

[turntaker]

Yes you do

What is your uni goal

 

[1008]

Someone please to me oxidation and reduction. I know OILRIG but I need specific examples with detailed explanation

Thanks

Oxidation and reduction aren't two separate reactions: they are 1 reaction, called a redox reaction. So, like in every chemical reaction, the atoms of different elements/compounds rearrange themselves and form new elements compounds.

This is done mainly by swapping electrons. Oxidation and reduction attempts to explain to us what really is going on when these compounds form and tries to justify why certain compounds were formed (and not others). E.g. in the dry cell:

The reason Zinc hydroxide and magnesium hydroxide are formed is because we know from the oxidation half equation at the anode that Zn reacts with the hydroxide ions to form zinc hydroxide, and releases 2 electrons in the process.

Now these electrons flow to the cathode, where they react with water and Magnesium (just realised there is an error in the photo, it is meant to be Mg not Mn) to form Magnesium hydroxide. The reason the electrons flow towards these compounds is because the reaction at the cathode is "reducing" (aka absorbing) all the electrons in the whole system due to the chemical reaction at the cathode, and so can be thought of as having a positive charge. Electrons have a negative charge and so are attracted towards anything positive. Overall, you can just write this reaction as one equation (refer to third equation in photo).

Although, as a general rule, metals tend to oxidise and donate electrons and non-metals tend to reduce and absorb electrons, this isn't always the case. But thank BOSTES, they provide you with the table of standard potentials present at the back of the periodic table they provide in the HSC (Hence Sien's suggestion). This table lists all the oxidation/reduction reactions relevant to the HSC course, so you won't have to memorise which elements oxidise and which reduce given a certain redox system.

 

[eyeseeyou]

I need examples and detailed explanation

Also need help with half equations and spectator ions

Need help with this

 

[eyeseeyou]

Oxidation and reduction aren't two separate reactions: they are 1 reaction, called a redox reaction. So, like in every chemical reaction, the atoms of different elements/compounds rearrange themselves and form new elements compounds.

This is done mainly by swapping electrons. Oxidation and reduction attempts to explain to us what really is going on when these compounds form and tries to justify why certain compounds were formed (and not others). E.g. in the dry cell:

The reason Zinc hydroxide and magnesium hydroxide are formed is because we know from the oxidation half equation at the anode that Zn reacts with the hydroxide ions to form zinc hydroxide, and releases 2 electrons in the process.

Now these electrons flow to the cathode, where they react with water and Magnesium (just realised there is an error in the photo, it is meant to be Mg not Mn) to form Magnesium hydroxide. The reason the electrons flow towards these compounds is because the reaction at the cathode is "reducing" (aka absorbing) all the electrons in the whole system due to the chemical reaction at the cathode, and so can be thought of as having a positive charge. Electrons have a negative charge and so are attracted towards anything positive. Overall, you can just write this reaction as one equation (refer to third equation in photo).

Although, as a general rule, metals tend to oxidise and donate electrons and non-metals tend to reduce and absorb electrons, this isn't always the case. But thank BOSTES, they provide you with the table of standard potentials present at the back of the periodic table they provide in the HSC (Hence Sien's suggestion). This table lists all the oxidation/reduction reactions relevant to the HSC course, so you won't have to memorise which elements oxidise and which reduce given a certain redox system.

Cheers

 

[eyeseeyou]

Oxidation and reduction aren't two separate reactions: they are 1 reaction, called a redox reaction. So, like in every chemical reaction, the atoms of different elements/compounds rearrange themselves and form new elements compounds.

This is done mainly by swapping electrons. Oxidation and reduction attempts to explain to us what really is going on when these compounds form and tries to justify why certain compounds were formed (and not others). E.g. in the dry cell:

The reason Zinc hydroxide and magnesium hydroxide are formed is because we know from the oxidation half equation at the anode that Zn reacts with the hydroxide ions to form zinc hydroxide, and releases 2 electrons in the process.

Now these electrons flow to the cathode, where they react with water and Magnesium (just realised there is an error in the photo, it is meant to be Mg not Mn) to form Magnesium hydroxide. The reason the electrons flow towards these compounds is because the reaction at the cathode is "reducing" (aka absorbing) all the electrons in the whole system due to the chemical reaction at the cathode, and so can be thought of as having a positive charge. Electrons have a negative charge and so are attracted towards anything positive. Overall, you can just write this reaction as one equation (refer to third equation in photo).

Although, as a general rule, metals tend to oxidise and donate electrons and non-metals tend to reduce and absorb electrons, this isn't always the case. But thank BOSTES, they provide you with the table of standard potentials present at the back of the periodic table they provide in the HSC (Hence Sien's suggestion). This table lists all the oxidation/reduction reactions relevant to the HSC course, so you won't have to memorise which elements oxidise and which reduce given a certain redox system.

Why?

 

[1008]

Why?

Think about it this way: the hydroxide ion has a negative charge (hence it has 1 excess electron). So two hydroxide ions would have a charge of -2 (2 extra electrons). When the 2 hydroxides bond with zinc (which has no extra electrons and so a charge of 0), zinc gives away 2 of its electrons and absorbs the two hydroxides instead, forming zinc hydroxide. The 2 electrons that zinc donates have now been released.

 

[eyeseeyou]

Think about it this way: the hydroxide ion has a negative charge (hence it has 1 excess electron). So two hydroxide ions would have a charge of -2 (2 extra electrons). When the 2 hydroxides bond with zinc (which has no extra electrons and so a charge of 0), zinc gives away 2 of its electrons and absorbs the two hydroxides instead, forming zinc hydroxide. The 2 electrons that zinc donates have now been released.

You are awesome, thanks so much

 

[1008]

No worries

 

[eyeseeyou]

No worries

Guys rep 1008 like how you'd all rep Integrand