AS Chemistry- helping each other out!

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Reply 2540

User1686961

Original post by NutE

what do you mean? :smile:

Did you do OCR A F322 last year?

Reply 2541

NutE

Original post by ThatGuyRik

Did you do OCR A F322 last year?

nope, AQA

Reply 2542

samb1234

Original post by langlitz

No it's not 'technically correct'... both the bromoalcohol and dibromoalkane form via the bromonium ion intermediate.

I hadn't actually looked at his mechanism. I was just saying that some dibromoalkane would be produced it would just be the minor product

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Reply 2543

Supermanxxxxxx

What do you think full ums is for edexcel unit 1

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Reply 2544

_NMcC_

Original post by Amethyst-Wolf

Thanks _NMcC_ ! Thats super helpful :smile:

No problem!

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Reply 2545

hibaj

hey

whats the mark scheme definition for

enthalpy change of reaction,
enthalpy change of formation,
enthalpy change of combustion;\

??

thanks

Reply 2546

frozo123

Original post by samb1234

I hadn't actually looked at his mechanism. I was just saying that some dibromoalkane would be produced it would just be the minor product

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yes^

Reply 2547

C0balt

Original post by hibaj

hey

whats the mark scheme definition for

enthalpy change of reaction,
enthalpy change of formation,
enthalpy change of combustion;\

??

thanks

Enthalpy change when the amount shown in the equation react under standard condition 298K 100kPa

Enthalpy change when a mole of compound in standard state is formed from it's constituent elements in standard states under standard condition

Enthalpy change when a mole of a compound or an element reacts with oxygen completely

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Reply 2548

hibaj

Original post by C0balt

thanks!

Reply 2549

Windowswind123

On "q=mc(deltaT)" questions the unit for temperature in the mark-scheme is degrees Celsius. Surely if the units for specific heat capacity is JK^-1g^-1, then temperature should be measured in Kelvin?

Reply 2550

langlitz

Original post by Dylann

No it's not "wrong" because it would get you the marks in an AS exam. Hey, look at the title of this thread, it says AS!! Not Advanced Highers!

sorry yeah I was thinking this was an A level thread for some reason. I still don't think simplifying it by making it wrong is helping anyone. It's not even any simpler really

Reply 2551

annie79

Original post by C0balt

thats makes more sense
teacher wtf

COBALTTTT pls check ur inbox :biggrin:

thnxx

Reply 2552

frozo123

Original post by Windowswind123

On "q=mc(deltaT)" questions the unit for temperature in the mark-scheme is degrees Celsius. Surely if the units for specific heat capacity is JK^-1g^-1, then temperature should be measured in Kelvin?

if you think about it the difference between the temperatures in Kelvin is exactly the same as the difference in temperature in celsius, theoretically you are meant to work in Kelvin but this missed out step would not alter your answer :smile:

Reply 2553

Windowswind123

Ah yes, I was adding 273 to the temperature in Celsius. But of course as it is a change it would be the same. Thanks for that.

Reply 2554

gabby07

Hi can someone please explain these two questions for me? Thanks :biggrin:

1) How many unpaired electrons does a does a Nitrogen atom in its ground state have?

2) When 0.1mol of atoms of an element reacts with chlorine there is an increase in mass of 7.1g. A student is told the element could be Carbon, Sodium, Magnesium or Aluminium. What is the element?

Especially the second one I'm not sure about! Thanks

Reply 2555

C0balt

Original post by gabby07

Hi can someone please explain these two questions for me? Thanks :biggrin:

N has electronic configuration of 1s2 2s2 2p3 and in p orbital the three electrons are unpaired

Where can the increase in mass come from? Only chlorine. So calculate the number of moles of chlorine atoms (well they are ions but molar mass is the same anyway) in that compound
See the ratio of 0.1mol and the amount of chlorine and you will see

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Reply 2556

gabby07

Original post by C0balt

Ah lovely!! How did you know the mass increase is solely down to the chlorine. That is what didn't occur to me when doing the question... :redface:

Reply 2557

C0balt

Original post by gabby07

Ah lovely!! How did you know the mass increase is solely down to the chlorine. That is what didn't occur to me when doing the question... :redface:

How..? Well it couldn't be anything else XD
Also the question was asked many times so I don't even remember how and when I first realised it haha

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Reply 2558

VetVikki

Anyone doing AQA: What do we need to know for this point of the spec .. can't find anything in my notes

"know that early models of atomic structure predicted thatatoms and ions with noble gas electron arrangementsshould be stable"

Reply 2559

annie79

Original post by gabby07

Ah lovely!! How did you know the mass increase is solely down to the chlorine. That is what didn't occur to me when doing the question... :redface:

its saying the INCREASE in mass, not what the final mass of the atoms and chlorine is combined. The INCREASE in mass after the two have REACTED is due to the ADDITION of Cl because that's the only thing that can cause the increase in mass because the ATOMS stay the SAME. so you do 7.1/35.5 = 0.2 moles of cl. ratio of atoms to Cl is: 1:2, so atom has to be +2!

I was also stuck on this Q, but I literally only JUST got it by reading your post!!

Thing i don't understand, is why you divide 7.1g by 35.5 and not by 71 since Cl2 is diatomic O.o maybe Cobalt can explain :smile: