A-level Chemistry Revision Squad!
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Original post by PlayerBB
I think we use ethanol, I am not sure though but I guess we don't use it all the time like for aromatic substitution reaction, we use NaOH so I think the concept is that we use alcholos
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Oh i meant is the haloalkane dissolved in ethanol or the nucleophile dissolved in ethanol? - AS chemistry btw
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Original post by kiiten
Oh i meant is the haloalkane dissolved in ethanol or the nucleophile dissolved in ethanol? - AS chemistry btw
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Oh I guess, nucleophile dissolved in ethanol.
Are you stuck on a specific past paper question or sth ?
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Whats sth? - no i got confused because in my textbook it says the nucleophile is dissolved in ethanol then the haloalkane is added. But, ive seen before (cant remember where) the haloalkane is dissolved in ethanol. :s
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Original post by kiiten
Whats sth? - no i got confused because in my textbook it says the nucleophile is dissolved in ethanol then the haloalkane is added. But, ive seen before (cant remember where) the haloalkane is dissolved in ethanol. :s
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(Something) and I don't know, I don't wanna say something that is 50% wrong
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Hi guys, Could someone possibly help me answer this! 2) Identify the white solid and write and equation for the formation in this reaction. Explain why the reaction of calcium and sulphuric acid stopped even though some calcium remained
White solid____________________________________________________________________
Equation______________________________________________________________________
Explanation_____________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3) A Grignard reagent is a compound in which magnesium is bonded to an alkyl group (R) and a halogen (X). It can be represented by the formula RMgX. A Grignard reagent is formed by the reaction of magnesium metal with haloalkane using dry ethoxyethane as a solvent. Ethoxyethane has a boiling point of 35 centigrade, forms a dense vapour and is highly flammable.
Give one reason why a hot water bath is used rather than direct heating with a bunsen burner when preparing the Grignard reagent
1.
A reaction of calcium with sulphuric acid was faster than the reaction of magnesium with HCL. However the reaction of calcium with sulphuric acid soon stopped even though some calcium remained. A white solid formed. Give two reasons why the reaction was faster at first with calcium and sulphuric acid than with magnesium and hydrochloric acid
White solid____________________________________________________________________
Equation______________________________________________________________________
Explanation_____________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3) A Grignard reagent is a compound in which magnesium is bonded to an alkyl group (R) and a halogen (X). It can be represented by the formula RMgX. A Grignard reagent is formed by the reaction of magnesium metal with haloalkane using dry ethoxyethane as a solvent. Ethoxyethane has a boiling point of 35 centigrade, forms a dense vapour and is highly flammable.
Give one reason why a hot water bath is used rather than direct heating with a bunsen burner when preparing the Grignard reagent
Original post by PlayerBB
First you have to find the Empirical formula, the question gave you the percentage of each atom, those percentages ads to 100 which means there is no other atom but C,H
You treat the percentages as the masses of each atom, okay so to find the number of moles, Mass/Mr , then you divide on the smallest number of moles to find the mole ratio, the numbers have to be integers.
To find the molecular formula, you need to find n which is the Mr of molecular formula/Mr of empirical formula
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You treat the percentages as the masses of each atom, okay so to find the number of moles, Mass/Mr , then you divide on the smallest number of moles to find the mole ratio, the numbers have to be integers.
To find the molecular formula, you need to find n which is the Mr of molecular formula/Mr of empirical formula
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'To find the molecular formula, you need to find n which is the Mr of molecular formula/Mr of empirical formula' so how am i meant to find out the mr of the molecular formula if i dont even know what the molecular formula is ?
sorry if this sounds stupid
are you not meant to work the shape of molecule of so4 2- like this:
6+4+2=12
12/2=6
therefore 4 bonding pairs and 2 lone pairs so the shape should be a square planer with a bond angle of 90
but i dont get why the answer is a tetrehedral woth a bond angle of 109.5
6+4+2=12
12/2=6
therefore 4 bonding pairs and 2 lone pairs so the shape should be a square planer with a bond angle of 90
but i dont get why the answer is a tetrehedral woth a bond angle of 109.5
Original post by itsastudentyo
Thank you so much....im still a little bit confused tho you said
'To find the molecular formula, you need to find n which is the Mr of molecular formula/Mr of empirical formula' so how am i meant to find out the mr of the molecular formula if i dont even know what the molecular formula is ?
sorry if this sounds stupid
'To find the molecular formula, you need to find n which is the Mr of molecular formula/Mr of empirical formula' so how am i meant to find out the mr of the molecular formula if i dont even know what the molecular formula is ?
sorry if this sounds stupid
No, it's not stupid at all, and in the question if you read it again, it says that Mr of the molecular formula is 114
Original post by K3001N
Hi guys, Could someone possibly help me answer this! 2) Identify the white solid and write and equation for the formation in this reaction. Explain why the reaction of calcium and sulphuric acid stopped even though some calcium remained
White solid____________________________________________________________________
Equation______________________________________________________________________
Explanation_____________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3) A Grignard reagent is a compound in which magnesium is bonded to an alkyl group (R) and a halogen (X). It can be represented by the formula RMgX. A Grignard reagent is formed by the reaction of magnesium metal with haloalkane using dry ethoxyethane as a solvent. Ethoxyethane has a boiling point of 35 centigrade, forms a dense vapour and is highly flammable.
Give one reason why a hot water bath is used rather than direct heating with a bunsen burner when preparing the Grignard reagent
1.
A reaction of calcium with sulphuric acid was faster than the reaction of magnesium with HCL. However the reaction of calcium with sulphuric acid soon stopped even though some calcium remained. A white solid formed. Give two reasons why the reaction was faster at first with calcium and sulphuric acid than with magnesium and hydrochloric acid
White solid____________________________________________________________________
Equation______________________________________________________________________
Explanation_____________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3) A Grignard reagent is a compound in which magnesium is bonded to an alkyl group (R) and a halogen (X). It can be represented by the formula RMgX. A Grignard reagent is formed by the reaction of magnesium metal with haloalkane using dry ethoxyethane as a solvent. Ethoxyethane has a boiling point of 35 centigrade, forms a dense vapour and is highly flammable.
Give one reason why a hot water bath is used rather than direct heating with a bunsen burner when preparing the Grignard reagent
You should try to solve them, even if you think maybe the answer is wrong and we're supposed to guide you or tell you where you went wrong but not solve a whole homework question for you
Original post by kiiten
What does the free radical substitution mechanism look like for methane + chlorine. I know the steps but don't know how to draw it :s
What about if you try to draw it and we will help you where you went wrong
Hi guys, here is a question ( question 2) http://papers.xtremepapers.com/CIE/C...1_s08_qp_5.pdf i have been trying to solve the entire day. It is about determining x in hydrous salt. Now what i did was plot mass of basic carbonate (y axis) against number of moles of carbonate (i.e (mass of CuO/(2 x 79.5)) I wrote this considering the molar ratio of CuO and basic carbonate. And so the gradient of graph would give mass/mol= Mr of hydrous salt. So i did this but the mark scheme ( http://papers.xtremepapers.com/CIE/C...1_s08_ms_5.pdf ) says ignore any ref to moles. So idk, even if i plot mass of CuO against basic carbonate mass or reverse or in anyway as shown in the mark scheme as shown below, how do i calculate the value of x? can somebody please help me, while considering any of the option out of those given like how can we plot the graph/Please help asap
Anyone thats doing the OCR B Salters course do you have an attachment of the activity pack for each module, my school is closed for me to go and access it 
I was ready to finally tackle chemistry (been putting it off) for tomorrow, got my equipment and textbook and wrote down the things I need to work on in particular, saw Kc and now I've lost all the motivation. Help. 
(edited 8 years ago)
Original post by itsastudentyo
are you not meant to work the shape of molecule of so4 2- like this:
6+4+2=12
12/2=6
therefore 4 bonding pairs and 2 lone pairs so the shape should be a square planer with a bond angle of 90
but i dont get why the answer is a tetrehedral woth a bond angle of 109.5
6+4+2=12
12/2=6
therefore 4 bonding pairs and 2 lone pairs so the shape should be a square planer with a bond angle of 90
but i dont get why the answer is a tetrehedral woth a bond angle of 109.5
https://www.youtube.com/watch?v=f32ra5yjG0s
Original post by PlayerBB
What about if you try to draw it and we will help you where you went wrong
Sorry for bad diagram :s
Original post by kiiten
What does the free radical substitution mechanism look like for methane + chlorine. I know the steps but don't know how to draw it :s
Check your specification. You are unlikely to have to draw a mechanism with curly arrows. If you are expected to do this then you must use single headed arrows.
(edited 8 years ago)
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