Chemistry Problem (1 Viewer)

[hit patel]

Guys in Year 11 I used to find chemistry simple but now I find it confusing especially the multiple choice. Its almost as if all the content disappears from my brain when I do the question. For calculation or equilibrium things its ok, but for things like electrochemistry I find it confusing. What should I DO?
All Help MUCH APPRECIATED.

 

[enigma_1]

Heyy, got a sample question on you?

 

[Carrotsticks]

Guys in Year 11 I used to find chemistry simple but now I find it confusing especially the multiple choice. Its almost as if all the content disappears from my brain when I do the question. For calculation or equilibrium things its ok, but for things like oxidation or atomic number I find it so much confusing. What should I DO?
All Help MUCH APPRECIATED.

Do you understand the principles of stoichiometry?

 

[strawberrye]

Practice more multiple choice questions on areas of your weakness, remember to calm down, stop panicking, deconstruct the information given in the question and follow a series of steps to eliminate answers and select the most probable-the best answer for that question, I would strongly advise you to revise over your atomic numbers and oxidation/reduction processes in this case.

 

[hit patel]

Please show me how to do each one..... yes carrot, as I mentioned I am ok with calculations of moles, ph , molarity concentration etc. just the electrchemistry the oxidant etc. Strawberry by atomic numbers i meant the use of atomic numbers to determine the type of decays that will occur i.e. nuclear chemistry. How do you determine these things>?

 

[enigma_1]

Question 5

Unstable nuclei have neutron to proton ratios outside of the zone of stability. It’s not option (a) because low atomic number elements are usually stable as seen in the zone of stability. Option (d) is incorrect because n: p ratio of 1 : 1.1 is roughly stable. For an unstable element, the ratio must be greater than that.
By referring to theory, it is evident that an unstable element is one which has an atomic number of greater than 83 and hence that zones out (c ) so we are left with option (b) which has to be correct because elements with atomic number of greater than 83 are unstable and DO emit alpha radiation to get their n: p ratio in the zone of stability asap because alpha radiation emits helium.

Naming hydrocarbon question:

Longest carbon chain is 5 carbons, so –pentane
Halogens take precedence over methyl groups. Here there are 2 halogens. Since “B” comes before “F” you start off with the Bromo (stupid rule I know, but confirm with your school and how they mark and whether they do it alphabetically or not) So then it is 2-bromo-1,4-dichloro …
Then name the methyl groups. Counting from the RHS to LHS since the Bromine is there. So the methyl groups are on carbon 3 and 4.
:. The name is 2-bromo-1,4-dichloro-3,4-dimethylpentane which is option (a)



Having a look at the other questions now.

Btw, please check the answers to confirm!

 

[enigma_1]

Hahahah no worries

Naming IUPAC stuff:

1) Find the longest carbon chain (this will be your ending of the name eg -pentane)
2) Side chains/Double/Triple bonds: (Below dot points are listed in order of importance when naming)
- Double Bond
- Halogen (eg Br, F, Cl)
- Hydrocarbon side chain (eg methyl, ethyl)
[Number your carbons btw]

Just to add:
Dashes between numbers and letter
No space between letters
Commas between numbers

I'm annoyed at the last question though.. Someone please help

 

[enigma_1]

View attachment 30117
Please show me how to do each one..... yes carrot, as I mentioned I am ok with calculations of moles, ph , molarity concentration etc. just the electrchemistry the oxidant etc. Strawberry by atomic numbers i meant the use of atomic numbers to determine the type of decays that will occur i.e. nuclear chemistry. How do you determine these things>?

Apparently like heavier elements atomic no.>83 give off alpha radiation because it emits a helium nuclei and if you think about it and write an equation with it, you'll see that it becomes a smaller, more stable element much quicker than if it was emitting any other form of radiation. So alpha decay is only for heavy elements usually.

Beta decay is if you wanna increase the atomic number and is for smaller elements with atomic number less than 83.

I'm unsure of gamma radiation since it has no charge and mass :L

 

[HeroicPandas]

Bottom right question requires rote memorisation of precipitation rules and flame test colours
-Brick-red flame means calcium
-White precipitate with F ions means there are calcium ions
-Yellow precip with lead means there are iodide ions

Hence answer is D

NO UNDERSTANDING REQUIRED FOR THIS, just memory

 

[enigma_1]

Bottom right question requires rote memorisation of precipitation rules and flame test colours
-Brick-red flame means calcium
-White precipitate with F ions means there are calcium ions
-Yellow precip with lead means there are iodide ions

Hence answer is D

NO UNDERSTANDING REQUIRED FOR THIS, just memory

Mate, so where do we find these random pieces of info to rote learn anyway?

 

[HeroicPandas]

Mate, so where do we find these random pieces of info to rote learn anyway?

Jacaranda chemistry textbook

 

[enigma_1]

Cheers thanks