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Edexcel Chemistry Unit 1 (23/05/2013)

Reply 80

ayat94

has everyone finished there revision

Reply 81

ayat94

i still dont understand ppm please help

Reply 82

snowy173

Original post by ayat94

i still dont understand ppm please help

ppm is another way of measuring concentration

its the mass of something/ the volume its dissolved in x 1x10^6

Reply 83

Kurraiyo

7

Anyone has the Jan 2013 mark scheme for unit 1 please?? I can't find it anywhere :confused:

Reply 84

coolio41

8

Can someone help me with http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/January%202012%20-%20QP/6CH01_01_que_20120307.pdf

(January 2012)Question 13 please a and b, I don't really understand. Thank you in advance! :biggrin:

Reply 85

ayat94

why does atomic radius increase down the group

Reply 86

ayat94

IN QUESTION 13A)
use this formula
charge of the positive(cation ) x charge of negative
example in LIF
charge of Li is +1 and F is -1
so you times +1 by -1 divide it by ionic radius if the anion +cation
the more negative the more exothermic

13b)just calculate difference of ionic radii
the greater the difference will give the answer

from my working out i have got the following answers
13a)c
13b)d

Reply 87

SophieL1996

2

help on jan 13 tick box queations: Q3, 5,7, :biggrin:

thanks

Reply 88

AnishaJayne

2

Original post by ayat94

why does atomic radius increase down the group

the addition of new shells mean that the outer electrons are further away from the nucleus, thus resulting in being less attracted. Therefore the protons are not pulling on the electrons as tightly.

The atomic radii decreases as you go along the period because the the number of protons in the nucleus of the atoms increase therefore this increase in positive charge means the outer electrons are being pulled in more tightly.

I hope that helps :smile:

Reply 89

Mollymod

15

Q3.

Original post by SophieL1996

help on jan 13 tick box queations: *Q3, 5,7, * :biggrin:

thanks

Mass/M_r = 16g divided by 32 (which is the M_r of O₂) as Oxygen is diatomic gives you 0.5
Do 0.5 x 6.02 x 10²³ = 3.0 x 10²³ which is D

Q5, Ionic equations are based on the ions involved in a reaction. So the charge particles in a reaction
This reaction is making a salt.
You know that Copper forms ions (most commonly of Cu²⁺) so it can't be B or C.
In all the reactions you form a silver precipitate. It's D because D is fully balanced and forms the right copper ion.
Ag just doesn't form 2

Reply 90

maryam1996

Original post by Mollymod

I'm a resitter, simply to boost up my grade for A2.
I'm doing Unit 5 in a month too, so Unit 1 is a good like memory jogger.
I really need full UMS in this if I want an A, so it's a tight margin.
Any questions, you can ask me and I'll do my best to try and answer them :smile:

Can you please help me, i don't understand question17)b)vi) from the 2013 Jan pastpaper, Suggest the formula of another metal ion which could form an alum, in combination with potassium and sulfate ions. ( The answer in the markscheme is Cr3+/ Fe3+/ Sc3+ / Ga3+Accept any feasible triply positive metal ion) but i don't really understand why we have to choose a metal with a +3 charge.). Thank you :smile:

Reply 91

casa12

Original post by ayat94

IN QUESTION 13A)
use this formula
charge of the positive(cation ) x charge of negative
example in LIF
charge of Li is +1 and F is -1
so you times +1 by -1 divide it by ionic radius if the anion +cation
the more negative the more exothermic

13b)just calculate difference of ionic radii
the greater the difference will give the answer

from my working out i have got the following answers
13a)c
13b)d

could you please explain question 13b further?

Reply 92

rainerised

9

how do you do q6 on jan 10?, the first ionisation energies of 4 elements with consecutive atomic numbers are shown: A 1680, B 2080, C 496 D 738, which element could be an inert gas, which element could be x in a covalent compound with formula HX and which element could be y in an ionic compound with formula YH2?

Reply 93

Mollymod

15

Original post by maryam1996

Can you please help me, i don't understand question17)b)vi) from the 2013 Jan pastpaper, Suggest the formula of another metal ion which could form an alum, in combination with potassium and sulfate ions. ( The answer in the markscheme is Cr3+/ Fe3+/ Sc3+ / Ga3+Accept any feasible triply positive metal ion) but i don't really understand why we have to choose a metal with a +3 charge.). Thank you :smile:

Read the information back at the top of Question 17.
It gives you a hint. An alum is Potassium Aluminium Sulphate.
So you've got the Sulphate, and you've got the Potassium. Obviously you can't pick Aluminium again.
What do all elements in Group 3 have in common? Three outer shell electrons on their structure. Therefore they'll react similar chemically, so you need something similar to Aluminium, and the only way you'll find that, is if you pick something in the same group or with the same charge. So if you know metal ions, such as chromium ions or iron ions, Gallium works here too, we're talking about something that will react the same as Aluminium chemically and ionically. So it's the 3+ charge that they want.

Reply 94

Mollymod

15

Original post by rainerised

how do you do q6 on jan 10?, the first ionisation energies of 4 elements with consecutive atomic numbers are shown: A 1680, B 2080, C 496 D 738, which element could be an inert gas, which element could be x in a covalent compound with formula HX and which element could be y in an ionic compound with formula YH2?

Inert gas will have highest Ionisation energy of the bunch, as it's stable and doesn't react, so it'll take loads of energy to remove its outer electron and get it to 'lose' its' 'happy/stable' state.

A is the answer to the second part because it's a covalent compound with 7 electrons in its outer shell, so the ionisation energy will be high (as it's nearly a full outer shell and would rather gain an electron than lose one as it's closer to being more stable that way) but it won't be as high as the inert gas one, so I chose the next-highest ionisation energy from the list.

6 electrons in its outer shell, so I'd say D because it's the third-highest ionisation energy for the same reason I gave above, but by process of elimination it's between C and D, and C is too low an ionisation energy for something that nearly has a full outer shell.

Reply 95

faz10420

I'm still getting confused during calculations involving diatomic molecules...when am I supposed to double the molecular mass and when am I not supposed to?

Reply 96

maryam1996

I have another question, can someone please help me. Why does the electron affinity become less exothermic as you go down group 7?
Thank you :smile:

Reply 97

rainerised

9

Original post by Mollymod

Inert gas will have highest Ionisation energy of the bunch, as it's stable and doesn't react, so it'll take loads of energy to remove its outer electron and get it to 'lose' its' 'happy/stable' state.

A is the answer to the second part because it's a covalent compound with 7 electrons in its outer shell, so the ionisation energy will be high (as it's nearly a full outer shell and would rather gain an electron than lose one as it's closer to being more stable that way) but it won't be as high as the inert gas one, so I chose the next-highest ionisation energy from the list.

6 electrons in its outer shell, so I'd say D because it's the third-highest ionisation energy for the same reason I gave above, but by process of elimination it's between C and D, and C is too low an ionisation energy for something that nearly has a full outer shell.

thanks

Reply 98

faz10420

Original post by maryam1996

I have another question, can someone please help me. Why does the electron affinity become less exothermic as you go down group 7?
Thank you :smile:

The first time you add an electron to a halogen, you're forming a more stable ion so the reaction is exothermic. After that, you're just trying to add electrons to a stable ion, and that requires energy, so subsequent electron affinities are endothermic. These then become more endothermic, because you keep trying to add negative electrons to a negative ion, which is increasingly difficult :smile:

Reply 99

rainerised

9

also how do you do q7 jan 10, it shows you a graph of second ionisation energies of a series of elements with consecutive atomic numbers and asks which could be lithium, the graph goes up from a-b then down from b-c then up from c-d?

second ie.png26.2KB

Edexcel Chemistry Unit 1 (23/05/2013)

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