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AQA Chemistry Unit 1 - [23rd May 2014]AM

lots of organic stuff, as usual probably. I have a feeling there will be some moles calculations in section B for some reason. Don't take my word on it though - I honestly have no idea :L Do you have any predictions?

shapes, periodicity.. Not sure either to be honest :L

Reply 181

meh jabeen

Can sum1 explain to me why the answer is second??

Question 5g) June 2013
Which one of the first second or third ionisations of thallium produces an ion with the electron configuration [Xe] 5d10 6s1

Reply 182

_Caz_

10

Original post by jack97

For naming the shapes, say you've got a a molecule with 4 electron pairs, consisting of 1 lone pair and 3 bonding pairs. Can we just name it as 'tetrahedral', or do we have to be specific like 'trigonal pyramid' due to the lone pair distorting the shape.

I thought tetrahedral was like CH4 molecules and trigonal pyramidal was Like ammonia (NH3 with lone pair?) I'm so bad at shapes...

Reply 183

sa97

2

Original post by Lucy5000

can someone help with may 2012 Q5a

Pressure has to be in Pascals and Volume in m3

PV=nRT
100,000 x 0.005 = n x 8.31 x 298

n = (100,000 x 0.005) / (8.31 x 298) = 0.2019...

n, the number of moles of gas in mixture of 2BCl3 + 3CO = 0.2019...

n, the number of moles in B2O3 = 0.2019.. / 5 = 0.0403..

Mass of B2O3 = Mr x n = 69.61 x 0.403... = 2.81g

(edited 9 years ago)

Reply 184

jack97

10

Original post by _Caz_

I thought tetrahedral was like CH4 molecules and trigonal pyramidal was Like ammonia (NH3 with lone pair?) I'm so bad at shapes...

no, if a molecule has a lone pair then it changes its shape due to the repulsion, thats why im wondering whether we can just say tetrahedal for a molecule with 3 bonding pairs and 1 lone pair, or do we have to call it a trigonal pyramid.

Reply 185

cams101

Original post by jack97

no, if a molecule has a lone pair then it changes its shape due to the repulsion, thats why im wondering whether we can just say tetrahedal for a molecule with 3 bonding pairs and 1 lone pair, or do we have to call it a trigonal pyramid.

Just call it bent or v-shaped

Reply 186

Lucy5000

Original post by sa97

Pressure has to be in Pascals and Volume in m3

PV=nRT
100,000 x 0.005 = n x 8.31 x 298

n = (100,000 x 0.005) / (8.31 x 298) = 0.2019...

n, the number of moles of gas in mixture of 2BCl3 + 3CO = 0.2019...

n, the number of moles in B2O3 = 0.2019.. / 5 = 0.0403..

Mass of B2O3 = Mr x n = 69.61 x 0.403... = 2.81g

thanx but why do I multiply number of moles in b2o3 by 5? Where is the 5 coming from?

let me rephrase that. Why am I diving by 5? "The number of moles in b2o3 = 0.2019/5. Confused how you got 5?

(edited 9 years ago)

Reply 187

Tom Riddle

Original post by jack97

no, if a molecule has a lone pair then it changes its shape due to the repulsion, thats why im wondering whether we can just say tetrahedal for a molecule with 3 bonding pairs and 1 lone pair, or do we have to call it a trigonal pyramid.

If it says shape that the atoms make, say distorted trigonal pyramid.

Reply 188

Rooroo96

4

Original post by jack97

For naming the shapes, say you've got a a molecule with 4 electron pairs, consisting of 1 lone pair and 3 bonding pairs. Can we just name it as 'tetrahedral', or do we have to be specific like 'trigonal pyramid' due to the lone pair distorting the shape.

You have to say trigonal pyramidal!

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Reply 189

Jake97

9

Original post by jack97

For naming the shapes, say you've got a a molecule with 4 electron pairs, consisting of 1 lone pair and 3 bonding pairs. Can we just name it as 'tetrahedral', or do we have to be specific like 'trigonal pyramid' due to the lone pair distorting the shape.

both are on the markscheme dont worry

Reply 190

jack97

10

Original post by cams101

Just call it bent or v-shaped

sorry but thats wrong.

Reply 191

jack97

10

Original post by Jake97

both are on the markscheme dont worry

ok thanks, so does that go the same for octahedral?

4 Bonding, 2 Lone = 6 Electron Pairs, can i say octahedral or square planar
6 bonding = octahedral.

So i only need to know the 4 main shapes? Linear, trigonal planar, tetra, octa

Reply 192

cams101

Original post by jack97

sorry but thats wrong.

oh yeah lol thought it said 2 bonding pairs, my bad.

Reply 193

_Caz_

10

Original post by jack97

no, if a molecule has a lone pair then it changes its shape due to the repulsion, thats why im wondering whether we can just say tetrahedal for a molecule with 3 bonding pairs and 1 lone pair, or do we have to call it a trigonal pyramid.

Is this wrong then?

IMG_20140522_180505436.jpg167.2KB

Reply 194

username1426305

2

Original post by _Caz_

Is this wrong then?

thats right.

Reply 195

_Caz_

10

Original post by ThatMadClown

thats right.

Thanks

Reply 196

MP2205

1

Do we lose marks if we don't draw a wedge or dotted line to indicate the three dimensional structure when drawing shapes

Reply 197

_Caz_

10

Original post by jack97

ok thanks, so does that go the same for octahedral?

4 Bonding, 2 Lone = 6 Electron Pairs, can i say octahedral or square planar
6 bonding = octahedral.

So i only need to know the 4 main shapes? Linear, trigonal planar, tetra, octa

4 bonding 2 lone pairs would be square planar I should imagine. In the same way that 3 bonding 2 lone pairs is trigonal planar.

Reply 198

hereticalpilgrim

3

Someone help pls

I have an exam in the morning and it clashes with chemistry. So I'm doing chemistry in the afternoon, what happens when you're put in isolation? Are you allowed to revise during this period HELP

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Reply 199

_Caz_

10

Original post by MP2205

Do we lose marks if we don't draw a wedge or dotted line to indicate the three dimensional structure when drawing shapes