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March 29, 2024, 06:08:49 am

Author Topic: HSC Chemistry Question Thread  (Read 1040620 times)  Share 

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Happy Physics Land

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Re: Chemistry Question Thread
« Reply #630 on: August 14, 2016, 08:22:04 pm »
+1
Let's just proclaim the good news:

I AM WELL AND TRULY BACK BOYS
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jakesilove

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Re: Chemistry Question Thread
« Reply #631 on: August 15, 2016, 08:30:10 am »
+1
Let's just proclaim the good news:

I AM WELL AND TRULY BACK BOYS

The prodigal son has returned!
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anotherworld2b

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Re: Chemistry Question Thread
« Reply #632 on: August 15, 2016, 09:53:58 am »
0
Hi was wondering if I could get help with chromatography. I wasn't sure where to get information for these aspects. :-X

•Justify the use of a particular chromatography technique by considering
•the properties of the substances being separated,
•the amount of substance available for analysis
•the sensitivity of the equipment


Loki98

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Re: Chemistry Question Thread
« Reply #633 on: August 15, 2016, 01:18:56 pm »
0
Industrial Chemistry Questions:
What kind of molecule would a micelle be classified as?
How do you explain soap acting as a emulsifier with reference to the formation of micelles?

Happy Physics Land

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Re: Chemistry Question Thread
« Reply #634 on: August 15, 2016, 02:00:41 pm »
0
Industrial Chemistry Questions:
What kind of molecule would a micelle be classified as?
How do you explain soap acting as a emulsifier with reference to the formation of micelles?

Hey Loki!!!

Ohhhh okay we don't usually classify micelle as a molecule, rather I would say its just a mixture. A micelle is essentially a spherical structure where the hydrophobic hydrocarbon chain from soap is adsorbed (i.e. dissolved, attached) into grease/oil through dispersion force and the negatively charged hydrophilic carboxylate head interacts with water molecules through ion-dipole forces. This is how I would define as a micelle, and I attached an image below to show you what a micelle look like. Now why is it a mixture? Because nothing is reacted, nothing is consumed and its just simply soap molecules attached onto grease.



Ok so I will kinda explain emulsification to you in numbered steps so its clearer:
1. Soap molecules are dissolved in water
2. Hydrophilic head of soap ion interacts with water molecule through ion-dipole, hydrocarbon chain interacts with and dissolves into grease through dispersion forces
3. Surfactant molecules continue to adsorb into the grease, decreasing the surface tension between grease and water
4. Ion-dipole force, being a stronger intermolecular force than dispersion force, pulls grease off the surface and this forms spherical droplets known as micelles
5. The negatively charged heads on the soap repel each other, preventing grease and dirt from joining back together and this keeps micelles dispersed throughout the solution and therefore achieving the emulsifying action

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MysteryMarker

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Re: Chemistry Question Thread
« Reply #635 on: August 15, 2016, 09:18:54 pm »
0
Would the general equation for cellulose to glucose be

(n-1)H2O + n(-C6H10O6-) --> n(-C6H12O6)

or just the same reaction but instead of (n-1) H2O its just H2O

Just a bit confused ;P

RuiAce

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Re: Chemistry Question Thread
« Reply #636 on: August 15, 2016, 10:02:59 pm »
0
Would the general equation for cellulose to glucose be

(n-1)H2O + n(-C6H10O6-) --> n(-C6H12O6)

or just the same reaction but instead of (n-1) H2O its just H2O

Just a bit confused ;P
(n-1) is correct.

Just remember: For your cellulose, the n is a subscript under the dash (a bit hard to demonstrate on forums):
-(C6H10O5)n-

And when it's glucose there's no need for a dash obviously

Maz

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Re: Chemistry Question Thread
« Reply #637 on: August 15, 2016, 11:40:13 pm »
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Hey,
I have a test coming up on soap and detergents, would you know any common questions that come up on a topic like that? or any things I should watch out for?

Thankyou :)
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Happy Physics Land

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Re: Chemistry Question Thread
« Reply #638 on: August 16, 2016, 08:15:26 pm »
+2
Hey,
I have a test coming up on soap and detergents, would you know any common questions that come up on a topic like that? or any things I should watch out for?

Thankyou :)

Hey mq123!

They can ask you various forms of questions about soaps and detergents that can largely be summed up in six categories:

- Explain how soaps are produced through saponification
- Explain the cleaning action of soaps/detergents
- Explain why detergents have been developed to replace soaps
- Explain the uses of soaps and detergents, in relation to their properties
- Explain how soaps/detergents act as emulsifiers
- Assess/Discuss the environmental and social impacts of soaps and detergents

What I recommend, along with knowing how to verbally address these questions, is to know how to draw the chemical composition of soaps/detergents (anionic cationic and non-ionic), or at least, their skeletal structure. With soaps you need to ensure that you include your carboxylate head group. With anionic detergents, make sure you include the sulfonate head group. With cationic detergents, make sure you include the quarternary ammonium group. Finally with non-ionic detergents you may like to show the hydroxyl head group. These are what distinguishes the types of detergents and their different uses and properties would rely on the function of these head groups.
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conic curve

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Re: Chemistry Question Thread
« Reply #639 on: August 17, 2016, 01:01:40 pm »
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Need help with the following

1. A student dissolves 5.3g of anhydrous sodium carbonate (Na2CO3) in water and then adds more water to make the volume up to 125 ml
a)why did the student first dissolve it on water and then make up the final volume by adding water
b)Why did the student use Anhydrous Na2CO3?

2. Calculate how many grams of solute are in 500mL of 0.5mol L^-1 sodium cholride (nacl) solution

Thanks Guys ;D

anotherworld2b

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Re: Chemistry Question Thread
« Reply #640 on: August 18, 2016, 06:24:37 pm »
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Hi I was wondering how do you write precipitation reactions?
I am confused on how cations and anions are involved in the reaction?
I am overall confused in general ???

RuiAce

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Re: Chemistry Question Thread
« Reply #641 on: August 18, 2016, 06:33:53 pm »
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Hi I was wondering how do you write precipitation reactions?
I am confused on how cations and anions are involved in the reaction?
I am overall confused in general ???
What do you mean by how to "write" precipitation reactions? You write them the same way you write everything else.

Also a cation is just an ion that has a positive charge (e.g. Na+) whereas an anion is an ion with a negative charge (e.g. Cl-)
They're not really important either unless you meant "ionic" equations.

conic curve

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Re: Chemistry Question Thread
« Reply #642 on: August 18, 2016, 08:12:07 pm »
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Hi I was wondering how do you write precipitation reactions?
I am confused on how cations and anions are involved in the reaction?
I am overall confused in general ???

I'm not exactly sure how cations and anions are involved in the reaction but all I know is that Cations and anions are formed when a metal loses electrons and a non metal gains those electrons (I don't know why that is the case). This then allows the electrostatic attraction between the positive charge and the negative charge to create an ionic compound

Read here for more: http://www.dummies.com/education/science/chemistry/positive-and-negative-ions-cations-and-anions/

Moderation edit: Removed tutoring service website link
« Last Edit: August 18, 2016, 08:13:45 pm by Aaron »

jyce

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Re: Chemistry Question Thread
« Reply #643 on: August 18, 2016, 08:30:41 pm »
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Hi I was wondering how do you write precipitation reactions?
I am confused on how cations and anions are involved in the reaction?
I am overall confused in general ???

Cations and anions are indeed involved in precipitation reactions. A precipitation reaction occurs when a positive ion (i.e., a cation) and a negative ion (i.e., an anion) combine to form an insoluble salt (the precipitate).

e.g., Ag+(aq) + Cl-(aq) -> AgCl(s)

RuiAce

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Re: Chemistry Question Thread
« Reply #644 on: August 18, 2016, 10:43:07 pm »
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Cations and anions are indeed involved in precipitation reactions. A precipitation reaction occurs when a positive ion (i.e., a cation) and a negative ion (i.e., an anion) combine to form an insoluble salt (the precipitate).

e.g., Ag+(aq) + Cl-(aq) -> AgCl(s)
That being said, this is an example of an ionic equation.