Amount of Substance | Multiple Choice Question Walkthrough 1 | A level Chemistry

[@toxicmalone770]

Watching this right before exams 😭This is so helpful! Thanks!!

[@chemistrytutor]

That's great to know thank you 😊 And the best of luck to you!

[@excellenceeminue1835]

Please could you tell me how is one supposed to know that buta-1,3-diene reacts with an alkene to make an addition reaction? As I haven’t come across it in the specification or lesson

[@chemistrytutor]

I'm not totally clear what you're asking due to an autocorrect issue (I think). When you study the Alkenes topic, you will learn that one of the main reactions alkenes undergo is addition reactions (specifically electrophilic addition). In general, this is where one (usually) small molecule, e.g. a halogen, adds onto the alkene in the position where the double bond was. The double bond becomes a single bond. If there are 2 double bonds, this addition is likely to happen twice

[@excellenceeminue1835]

@@chemistrytutor ohh I haven't even studied that yet😅😅I might have to pre-read it thankyou

[@chemistrytutor]

@excellenceeminue1835 good news! I'm sure it'll make sense when you do!

[@belugakrueger]

life saver

[@chemistrytutor]

Thanks! Happy to save you!

[@yusafali7]

do u do specific tutoring?

[@chemistrytutor]

I do sometimes, yes. If you're interested you can email me on [e-mail]

[@karthithiru]

for question 5 how did u get the 2 to 3 ratio

[@chemistrytutor]

It's taken straight from the equation. The numbers in front of the formula for each chemical. They're called the coefficients or multipliers

[@karthithiru]

oh ok thanks. will they give equations like this but we must constuct and balance them?@@chemistrytutor

[@chemistrytutor]

@karthithiru sometimes, but more often you're given the full equation. If you're not given it, the ratio is likely to be 1:1. You maybe wouldn't be expected to write the fill equation but work out the ratio they react in

[@nvrsq-t1x]

In question 9, how do you know that there are 200cm3 of oxygen gas at the start?

[@chemistrytutor]

The question tells us that the butane is reacting with 0.2dm3 of oxygen, which is 200cm3

[@nvrsq-t1x]

@@chemistrytutor I'm sorry I mean for question 6 not 9

[@ar-mo7xc]

Is this AS

[@chemistrytutor]

Yes, AS 👍I've got lots of other AS videos if needed

[@glo457]

Why don't A and B dilute the base? Technically it sounds like they do

[@chemistrytutor]

They would dilute it, but they won't change the moles present. Bigger volume but less concentrated = same moles

[@nihadkaweesa6690]

I'm sorry but I think question 2 is wrong because you only worked out the moles and didn't work out the concentration, yet that is wat the question was asking for. I love your videos tho

[@chemistrytutor]

Dont worry, it is correct 🙂 I never worked out conc = mol/volume, but in my third step I worked out the concentration in g/dm3 and then I divided it by Mr to get mol/dm3 But you're right. An alternative method could have been to work out moles and then divide by 0.1dm3

[@nihadkaweesa6690]

Oh yeah, my bad Thank you, I was a bit confused but I get it now 😊