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AQA AS Chemistry unit 1 resit May 27th 2016

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Trend of Ionisation Energy across period 3: Increases

Exception: Sulfur due to electron pair repulsion in 3p Orbital

Element Y: Sulfur, as biggest difference in successive ionisation energies are between 6th and 7th ionisation. Normal electron configuration of Sulfur : 1S²2S²2P⁶3S²3P⁴
Electron configuration of the ion from which the 7th ionisation energy occurs: 1S²2S²2P⁶which means element Y must be Sulfur.

Element with highest melting point in Period 3: Silicon due to giant covalent structure and many, strong covalent bonds which reuqire a lot of energy to break. No other element in Period 3 has a giant covalent structure.

Reply 161

Danny786

Y was sulfur

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Reply 162

Studious_Student

I got 42.3% for the percentage yield. But I used 3 significant figures during the calculation.

Reply 163

Charco63

Original post by berries366

Yeah thats right I think

107 is for trigonal pyramid which has 3 bonding pairs and a lone pair, SF4 has 4 bonding Pairs and a lone pair so it can't have been 107

Reply 164

Ultracrepidarian

Original post by Charco63

107 is for trigonal pyramid which has 3 bonding pairs and a lone pair, SF4 has 4 bonding Pairs and a lone pair so it can't have been 107

i thought it was 90

Reply 165

Raizelcadres

Original post by Danny786

Sf6 is 90 and other one was 107 I think????

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Yes, the mark scheme states anything from 106-107.5( I think) but I wrote 107.5 as the lone pair reduces the bond angle of 109.5 by 2 :smile:

Reply 166

Danny786

Original post by Raizelcadres

Yes, the mark scheme states anything from 106-107.5( I think) but I wrote 107.5 as the lone pair reduces the bond angle of 109.5 by 2 :smile:

That's what I assumed

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Reply 167

fariha97

Original post by danni1998

I said put both in water since methanol would dissolve as it forms H bonds with water whereas the other one (Methanethiol) or something would be insoluble?

That's exactly what I said

Reply 168

Hello123Anonym

Methanol has a higher boiling point than Methanethiol due to O-H (hydrogen bonding) being the strongest IMF as oppose to the weak VdW / dipole-dipole forces of attraction in Methanethiol, hence Methanol requires a greater input of energy to overcome its stronger IMF as oppose to Methanethiol.

Can be separated using fractional distillation due to differing boiling points.

Methanethiol has a smaller Mr than Selenol, and thus fewer Van der Waals forces of attraction between the molecules, which needs less energy to overcome. Hence, Selenol has a higher boiling point.

Reply 169

Emad1993

Original post by Studious_Student

I got 42.3% for the percentage yield. But I used 3 significant figures during the calculation.

you mean 49.3 % ?

Reply 170

Charco63

Original post by Raizelcadres

Yes, the mark scheme states anything from 106-107.5( I think) but I wrote 107.5 as the lone pair reduces the bond angle of 109.5 by 2 :smile:

107 is for 3 bonding pairs and 1 lone pair

Reply 171

Ultracrepidarian

Original post by Emad1993

you mean 49.3 % ?

how did you get that what did you divide 1.09 by

Reply 172

Charco63

Original post by Ultracrepidarian

i thought it was 90

I put 89 for SF4 not sure if it I right though

Reply 173

A2LEVELSHELPME

SF4 117.5 ?
it didnt ask for the shape of it though right?

Reply 174

Raizelcadres

Original post by Charco63

107 is for trigonal pyramid which has 3 bonding pairs and a lone pair, SF4 has 4 bonding Pairs and a lone pair so it can't have been 107

Doesn't a tetrahedral have 4 bonds and angle of 109.5 and when their is a lone pair it reduces by 2 that's how I came to 107.5. I'm not entirely sure.

Reply 175

Ultracrepidarian

Original post by A2LEVELSHELPME

SF4 117.5 ?
it didnt ask for the shape of it though right?

as in it asked you to draw the shape

Reply 176

Rid123

For mass spec question I put
Similarity-same number of detections as the number of electrons doesn't change only energy.
Difference- more peaks with lower m/z as higher energy electrons means more chance of second ionisations

(I thought this question could be similar to the photoelectric effect questions when the say the effect of increase photon energy)

Reply 177

97Y

Original post by MotorboatMyGoat

Same.

Did you get the empirical formula as Ca3C2O8H2?

Yeah, but I have a feeling that I wrote Cu by accident.. But I got those numbers

Reply 178

Ultracrepidarian

Original post by Raizelcadres

Doesn't a tetrahedral have 4 bonds and angle of 109.5 and when their is a lone pair it reduces by 2 that's how I came to 107.5. I'm not entirely sure.