Ocr f321 23 may 2013~official discussion thread

Do you think just mentioning that the sample must be gaseous is too vague for the mark (had to be in the context of both carbon structures being solid)? If anyone can remember a past paper with a question like this, please tell me.

yes i think thats more right,i may be wrong with my awnser!

Reply 1001

Haque95

4

Sorry for reposting this, but it can be a major help to any future person(s) who may want to make the unofficial mark scheme
* Some of the questions and marks given may not be right *

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)

2a) Write out the electronic configuration for an atom of sulphur (1)
2b) What are the 2 main ions in Al2(SO3)3 (2)
2c) Why is N2SO4 described as a salt? (1)
Can't remember exact structure of question 2, but a titration type question was there.

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)

6a) Describe the reactivity of the group 2 metals with chlorine as you descend the group. (5)
6b) State why using graphite or diamond for the first ionisation energy for carbon was (unnecessary?) (1)
6c) 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)
- 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)
- What is the ion responsible for bleach?
- 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 1002

kelvinbeyioku

4

Original post by theCreator

No that is the correct answer. Why would 3 moles of acid mean that 3 moles of water is produced. assumptions like that cannot be made. If you look all the atoms are balanced on each side

but in your equation there are 15 O's on LHS, and 18 on RHS , im pretty sure

Reply 1003

Student296

8

Singlehandedly lowered the grade boundaries, yet again

Reply 1004

username1107833

2

Original post by Haque95

Sorry for reposting this, but it can be a major help to anyone future person(s) who want make the unofficial mark scheme
* Some of the questions and marks given may not be right *

I just remembered the phosphorus questions were all question 2, and the bleach questions were question 4. The nitrogen and all the bond angle questions were question 5, and so the carbon diamond questions were question 6

Reply 1005

TheSnail

17

I thought I was alright :smile:

With the no. of molecules I x5 as I thought there were 5 molecules *oops*....aah well, I had the 3.something in my workings so hopefully will only drop 1 :smile:

Reply 1006

jackitsme

Original post by Haque95

Sorry for reposting this, but it can be a major help to anyone future person(s) who want make the unofficial mark scheme
* Some of the questions and marks given may not be right *

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)

1B) was not 3 marks it was 1 or 2

Reply 1007

MathsNerd1

17

Original post by theCreator

I just remembered the phosphorus questions were all question 2, and the bleach questions were question 4. The nitrogen and all the bond angle questions were question 5, and so the carbon diamond questions were question 6