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Ocr f321 23 may 2013~official discussion thread

Help to anyone who's making an unofficial mark scheme, some of the questions and marks given may not be right though:

1a) Define relative isotopic mass. (2)
1b) Fill the table in for the atomic structure of a potassium atom and ion. (3)
1c) How many molecules are in 6.(something)g of SiCl4? (3)
1d) Draw the symbols for each particle shown in the ionic lattice structure of KCl. (2)

3a) A precipitation reaction was used to identify the iodide present in Potassium Iodide. State the reagent used for this reaction (1)
3b) Write the ionic equation to show the reaction between this reagent and the Iodide ion, including state symbols. (2)
3c) What colour would the precipitate containing the iodide ion show? (1)
3d) A mixture of potassium iodide and bromine was present in a solution. What solvent can be used to identify the presence of iodide in this solution? (1)

5a) Describe the reactivity of the group 2 metals with chlorine as you descend the group. (5)
5b) State why using graphite or diamond for the first ionisation energy for carbon was (unnecessary?) (1)
5c) Fill the boxes in of the table stating the properties of lithium, carbon and fluorine (6)

A few other random questions I can remember (in any order):

- A student suggested the bond angles in H-N-H would be larger in NH3BF3 than NH3, suggest why. (3 marker I think)
- What bond angles are present in the F-B-F in: i) BF3 ii) NH3BF3 (2)
- Phosphene gas reacts with oxygen to form P4010 and water. Write out the equation for this reaction. (1)
- Why does PH3 have a lower boiling point than NH3? (1)
- Why is N2SO4 described as a salt? (1)
- State the main types of intermolecular forces in NH3 and PH3 (2)
- Give the equation for the reaction between Aluminium Oxide and sulphuric acid, including state symbols. (2)
- Work out the number for X in (metal).XH2O
- Using oxidation numbers, state why the reaction of P4 was a disproportionation reaction (3)
- Write out the equation for the reaction between Chlorine and water. Explain why the litmus paper turned red. (2)
- Define 'dative covalent bond'. (1 or 2?)
- Using dot and cross diagrams, draw the bonding in NH3BF3 and label the dative covalent bond. (2)

(edited 10 years ago)

Reply 941

Liberty.

10

Original post by jackitsme

i just said carbon makes diamond and graphite,its the building block of them so carbon is used rather than blah blah

Considering it was about ionisation energy I went on one about that carbon in both states has the same electron configuration :confused:

Reply 942

username1107833

2

Original post by Freddy-Francis

i diviided by 3 :eek:

Ah unlucky mate, you had to times by 3

Reply 943

moonziggy

11

Original post by Fullycorporate

Are you sure the first equation is balanced equation correctly? Seems like there are too many hydrogens on the right side, think it should be 3H2O?

And Reaction of chlorine and water forms HOCL but im pretty sure HCLO is the same thing

im sure its 3 H2O

Reply 944

Freddy-Francis

9

Original post by Fullycorporate

Are you sure the first equation is balanced equation correctly? Seems like there are too many hydrogens on the right side, think it should be 3H2O?

And Reaction of chlorine and water forms HOCL but im pretty sure HCLO is the same thing

its 2Cl2 + 2H2O ---> 4HCL + O2

Reply 945

moonziggy

11

Original post by theCreator

Just remembered the whole of question 3 or something.

-Reagent was Silver Nitrate AgNO3

-If iodide was present, yellow precipitate would form

-To show it was a mixture of bromide and iodide ions we would add concentrated ammonia (NH3)

I totally forgot about the concentrated part, I wrote NH3, do you think i'll get the mark?

Reply 946

jackitsme

Original post by theCreator

Ah unlucky mate, you had to times by 3

i times it by 3 ? and then times it by 24000 which gave 108 ? tell me what i did wrong :L

Reply 947

MichaelP96

Original post by jackitsme

i just said carbon makes diamond and graphite,its the building block of them so carbon is used rather than blah blah

I said they're allotropes of carbon?

Reply 948

username1107833

2

Original post by Freddy-Francis

its 2Cl2 + 2H2O ---> 4HCL + O2

Again sorry that's wrong, it's:

Cl2 + H20 ---> HCl + HClO

Reply 949

jackitsme

Original post by moonziggy

I totally forgot about the concentrated part, I wrote NH3, do you think i'll get the mark?

ahh i wrote cyclohexene!! LOOL

Reply 950

jackitsme

Original post by MichaelP96

I said they're allotropes of carbon?

nice word,yep,basically they make the covelnt structures so yep a mark!

Reply 951

username1107833

2

Original post by moonziggy

I totally forgot about the concentrated part, I wrote NH3, do you think i'll get the mark?

Maybe, but I doubt it, because in the concentration of ammonia is very important in determining the ions present

Reply 952

LH78

Original post by Freddy-Francis

its 2Cl2 + 2H2O ---> 4HCL + O2

No, H2O + CL2 --> HCL + HCLO (chlorate (I))

Reply 953

MichaelP96

Original post by Freddy-Francis

i diviided by 3 :eek:

You had to times it my freind. There was a 3:1 ratio!

Reply 954

LH78

Original post by jackitsme

ahh i wrote cyclohexene!! LOOL

me too!!!!

Reply 955

username1107833

2

Original post by jackitsme

i times it by 3 ? and then times it by 24000 which gave 108 ? tell me what i did wrong :L

The multiplying by 3 and the multiplying by 24,000 are 2 seperate questions, i think you're getting confused. The volume of gas was 360cm^3 of PH3. But the volume of NaOH was 22.5