Ocr f321 23 may 2013~official discussion thread

i was thinking A is 50 from this time last year and jan 13

i think i have dropped 10 marks to the most.
15 -18 ums.:O
i need to smash f322 or i am staying at home for the next year and repeating college :O

Exactly as you just said now infact "but a solid precipitate of iodine and bromine based compounds?". This is the exact reason we use ammonia, because all the bromine ions would dissolve showing us relatively how much iodide ions the solution contained. Cyclohexane infact would not have even worked.

I thought it just had that idiotic verbose part question passage...

I thought the question subsequently followed in the following way: "The student then.... They noticed that...."
Am I wrong!?

Even so, I feel Cyclohexane is for when distinguishing displacement reactions; not necessarily precipitation formation react ions high was clearly stated.

I hope that it is right!
It was only natural! It didn't take long to think of!
If I write something down too fast, it means it definitely is natural!


Posted from TSR Mobile

No Jan 13 was probably the easiest one there has been and that was 49 so i'm guessing this will be 49 due to it being mostly resitters

1)i) The mass of an atom of an isotope of an element compared with 1/12th of the mass of an atom of carbon-12
ii) 41K+

Answers, in a random order ( can't remember question numbers)

-Volume of PH3 gas produced = 360cm^3
-Angles were 120* then 109.5*
-The student thought the angle would be larger because there are 4 bond pairs now (due to the dative covalent bond) giving a tetrahedral shape with 109.5* bond angle
-Group 2 reactions with chlorine were more vigorous as you went down the group because atomic radius increased and electron shielding increased making it easier to lose the outermost electrons
-Volume of NaOH i think it was, was 22.5cm^3
-Formula of reaction: Al203 (solid) + 3H2SO4 (aq.) ---> Al2(SO4)3 (aq.) + 6H20 (liquid)
-Main ions were Al(3+) and SO4(2-)
-Number of water molecules was 16
-1st Ionisation energy across period increased because nuclear charge increased and atomic radius decreased
-Number of SiCl4 molecules was 3.01*10^22
-Bleaching ion was ClO-
-Reaction of chlorine and water: Cl2 + H20 --> HCL + HCLO
-Litmus paper turned red because HCL is an acid

Are you an A2 student?

1a) Define relative isotopic mass. (2)the mass of an atom of an isotope compared with 1/12 of the mass of an atom of c-12



1b) Fill the table in for the atomic structure of a potassium atom and ion. (3)

39K 19protons 20 neutrons 19 electrons
41K+ 19p 22neut 18electrons


1c) How many molecules are in 6.(something)g of SiCl4? (3) 3.01 x10 ^22


1d) Draw the symbols for each particle shown in the ionic lattice structure of KCl. (2)

alternating k+ and Cl- Ions


3a) A precipitation reaction was used to identify the iodide present in Potassium Iodide. State the reagent used for this reaction (1) AgNO3


3b) Write the ionic equation to show the reaction between this reagent and the Iodide ion, including state symbols. (2)ag+(aq) + i-(aq)= agi(s)


3c) What colour would the precipitate containing the iodide ion show? (1)yellow


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)conc nh3

4) a) - Using oxidation numbers, state why the reaction of P4 was a disproportionation reaction (3)

P has been both reduced and oxidised. Oxidised from 0 to +3 and reduced from 0 to -1.

4b)


5a) Describe the reactivity of the group 2 metals with chlorine as you descend the group. (5)
-increase nuclear charge outweighed by increase atomic radius
-more shells;more electrons;more inner shielding effect by inner electrons;
decrease nuclear attraction. easier to remove outer elect to react with halogens. reactivity increases hence reaction more vigorous down the group


5b) State why using graphite or diamond for the first ionisation energy for carbon was (unnecessary?) (1)
Ionisation energy is the same because both measure when they are gaseous atoms ?


5c) Fill the boxes in of the table stating the properties of lithium, carbon and fluorine (6)


Li = electrostatic attraction between the positive metal ions and delocalised electrons
C = giant and the shared pair of electrons in the covalent bond
F2=Van der Waals and between other F2 atoms


- A student suggested the bond angles in H-N-H would be larger in NH3BF3 than NH3, suggest why. (3 marker I think)

NH3 has 3 bonding pairs 1 lone pair.
NH3BF3 has 4 bonding pairs.
Electron pairs repel.
Lone pairs repel more than bonding pairs (-2.5) and so H-N-H drawn in more slightly so smaller.


- What bond angles are present in the F-B-F in:
i) BF3 120
ii) NH3BF3 109.5 (2)


- Phosphene gas reacts with oxygen to form P4010 and water. Write out the equation for this reaction. (1).

4PH3 + 8O2 = 6H2O + P4O10


- Why does PH3 have a lower boiling point than NH3? (1) hydrogen bonding stronger than Van der Waall/dipole to dipole (I wrote VDW)



- Why is N2SO4 described as a salt? (1)
The H+ion in acid has been replaced by the positive metal Na+ ion


- State the main types of intermolecular forces in NH3 and PH3 (2)
Hydrogen bonding and dipole to dipole



- Give the equation for the reaction between Aluminium Oxide and sulphuric acid, including state symbols. (2)
Al2O3 (s)+ 3H2SO4(aq) -------- Al2(SO4)3 (aq) + 3 H2O (l)


- Work out the number for X in (metal).XH2O 0.321/ 0.0200= 16


- Write out the equation for the reaction between Chlorine and water. Explain why the litmus paper turned red. (2)acid produced, ph decreases, increas in h+

Cl2 + HCl --> HCl + HClO acid has H+ ions so acidic


- Define 'dative covalent bond'. (1 ) sharing of a pair of electrons between 2 covalently bonded atoms where one of the atoms supplies both electrons.


- Using dot and cross diagrams, draw the bonding in NH3BF3 and label the dative covalent bond. (2)

H3N->BF3
dative covalent donated by N to B

- main ions in Al2(SO4)3 (1)

Al3+ and SO4^ 2-

- Volume of PH3 gas produced = 360cm cubed
- 22.5 for another calculation
- bleaching ion ClO-


The questions are muddled up and the marks don't add up to 60 but couldn't think of anymore.

yeah.
you?

1a) Define relative isotopic mass. (2)the mass of an atom of an isotope compared with 1/12 of the mass of an atom of c-12



1b) Fill the table in for the atomic structure of a potassium atom and ion. (3)

39K 19protons 20 neutrons 19 electrons
41K+ 19p 22neut 18electrons


1c) How many molecules are in 6.(something)g of SiCl4? (3) 3.01 x10 ^22


1d) Draw the symbols for each particle shown in the ionic lattice structure of KCl. (2)

alternating k+ and Cl- Ions


3a) A precipitation reaction was used to identify the iodide present in Potassium Iodide. State the reagent used for this reaction (1) AgNO3


3b) Write the ionic equation to show the reaction between this reagent and the Iodide ion, including state symbols. (2)ag+(aq) + i-(aq)= agi(s)


3c) What colour would the precipitate containing the iodide ion show? (1)yellow


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)conc nh3

4) a) - Using oxidation numbers, state why the reaction of P4 was a disproportionation reaction (3)

P has been both reduced and oxidised. Oxidised from 0 to +3 and reduced from 0 to -1.

4b)


5a) Describe the reactivity of the group 2 metals with chlorine as you descend the group. (5)
-increase nuclear charge outweighed by increase atomic radius
-more shells;more electrons;more inner shielding effect by inner electrons;
decrease nuclear attraction. easier to remove outer elect to react with halogens. reactivity increases hence reaction more vigorous down the group


5b) State why using graphite or diamond for the first ionisation energy for carbon was (unnecessary?) (1)
Ionisation energy is the same because both measure when they are gaseous atoms ?


5c) Fill the boxes in of the table stating the properties of lithium, carbon and fluorine (6)


Li = electrostatic attraction between the positive metal ions and delocalised electrons
C = giant and the shared pair of electrons in the covalent bond
F2=Van der Waals and between other F2 atoms


- A student suggested the bond angles in H-N-H would be larger in NH3BF3 than NH3, suggest why. (3 marker I think)

NH3 has 3 bonding pairs 1 lone pair.
NH3BF3 has 4 bonding pairs.
Electron pairs repel.
Lone pairs repel more than bonding pairs (-2.5) and so H-N-H drawn in more slightly so smaller.


- What bond angles are present in the F-B-F in:
i) BF3 120
ii) NH3BF3 109.5 (2)


- Phosphene gas reacts with oxygen to form P4010 and water. Write out the equation for this reaction. (1).

4PH3 + 8O2 = 6H2O + P4O10


- Why does PH3 have a lower boiling point than NH3? (1) hydrogen bonding stronger than Van der Waall/dipole to dipole (I wrote VDW)



- Why is N2SO4 described as a salt? (1)
The H+ion in acid has been replaced by the positive metal Na+ ion


- State the main types of intermolecular forces in NH3 and PH3 (2)
Hydrogen bonding and dipole to dipole



- Give the equation for the reaction between Aluminium Oxide and sulphuric acid, including state symbols. (2)
Al2O3 (s)+ 3H2SO4(aq) -------- Al2(SO4)3 (aq) + 3 H2O (l)


- Work out the number for X in (metal).XH2O 0.321/ 0.0200= 16


- Write out the equation for the reaction between Chlorine and water. Explain why the litmus paper turned red. (2)acid produced, ph decreases, increas in h+

Cl2 + HCl --> HCl + HClO acid has H+ ions so acidic


- Define 'dative covalent bond'. (1 ) sharing of a pair of electrons between 2 covalently bonded atoms where one of the atoms supplies both electrons.


- Using dot and cross diagrams, draw the bonding in NH3BF3 and label the dative covalent bond. (2)

H3N->BF3
dative covalent donated by N to B

- main ions in Al2(SO4)3 (1)

Al3+ and SO4^ 2-

- Volume of PH3 gas produced = 360cm cubed
- 22.5 for another calculation
- bleaching ion ClO-


The questions are muddled up and the marks don't add up to 60 but couldn't think of anymore.

i think that there were a few calculations in there that you missed out but i cant really remember them

Resitters mainly take the january exam, so usually the january exams have a higher grade boundary than June where almost everyone takes it including the people who get U's, E's and D's. But yeah I'd agree with you being around 50.

Yes, have you got F325 or F324 or both?

I believe it was the last part of the question for that specific question. To be honest i can't remember the questions that perfectly (oddly set out paper), i just didn't think how NH3 could apply when the question already tells it is in solution form already (which is why i put cyclohexane - i totally understand the point of putting conc NH3)

It's a shame that we don't get separate exam papers as you would with say maths or geography exams, at least then we could study it with better accuracy. Hopefully somebody managed to get a copy.

1a) Define relative isotopic mass. (2)the mass of an atom of an isotope compared with 1/12 of the mass of an atom of c-12



1b) Fill the table in for the atomic structure of a potassium atom and ion. (3)

39K 19protons 20 neutrons 19 electrons
41K+ 19p 22neut 18electrons


1c) How many molecules are in 6.(something)g of SiCl4? (3) 3.01 x10 ^22


1d) Draw the symbols for each particle shown in the ionic lattice structure of KCl. (2)

alternating k+ and Cl- Ions


3a) A precipitation reaction was used to identify the iodide present in Potassium Iodide. State the reagent used for this reaction (1) AgNO3


3b) Write the ionic equation to show the reaction between this reagent and the Iodide ion, including state symbols. (2)ag+(aq) + i-(aq)= agi(s)


3c) What colour would the precipitate containing the iodide ion show? (1)yellow


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)conc nh3

4) a) - Using oxidation numbers, state why the reaction of P4 was a disproportionation reaction (3)

P has been both reduced and oxidised. Oxidised from 0 to +3 and reduced from 0 to -1.

4b)


5a) Describe the reactivity of the group 2 metals with chlorine as you descend the group. (5)
-increase nuclear charge outweighed by increase atomic radius
-more shells;more electrons;more inner shielding effect by inner electrons;
decrease nuclear attraction. easier to remove outer elect to react with halogens. reactivity increases hence reaction more vigorous down the group


5b) State why using graphite or diamond for the first ionisation energy for carbon was (unnecessary?) (1)
Ionisation energy is the same because both measure when they are gaseous atoms ?


5c) Fill the boxes in of the table stating the properties of lithium, carbon and fluorine (6)


Li = electrostatic attraction between the positive metal ions and delocalised electrons
C = giant and the shared pair of electrons in the covalent bond
F2=Van der Waals and between other F2 atoms


- A student suggested the bond angles in H-N-H would be larger in NH3BF3 than NH3, suggest why. (3 marker I think)

NH3 has 3 bonding pairs 1 lone pair.
NH3BF3 has 4 bonding pairs.
Electron pairs repel.
Lone pairs repel more than bonding pairs (-2.5) and so H-N-H drawn in more slightly so smaller.


- What bond angles are present in the F-B-F in:
i) BF3 120
ii) NH3BF3 109.5 (2)


- Phosphene gas reacts with oxygen to form P4010 and water. Write out the equation for this reaction. (1).

4PH3 + 8O2 = 6H2O + P4O10


- Why does PH3 have a lower boiling point than NH3? (1) hydrogen bonding stronger than Van der Waall/dipole to dipole (I wrote VDW)



- Why is N2SO4 described as a salt? (1)
The H+ion in acid has been replaced by the positive metal Na+ ion


- State the main types of intermolecular forces in NH3 and PH3 (2)
Hydrogen bonding and dipole to dipole



- Give the equation for the reaction between Aluminium Oxide and sulphuric acid, including state symbols. (2)
Al2O3 (s)+ 3H2SO4(aq) -------- Al2(SO4)3 (aq) + 3 H2O (l)


- Work out the number for X in (metal).XH2O 0.321/ 0.0200= 16


- Write out the equation for the reaction between Chlorine and water. Explain why the litmus paper turned red. (2)acid produced, ph decreases, increas in h+

Cl2 + HCl --> HCl + HClO acid has H+ ions so acidic


- Define 'dative covalent bond'. (1 ) sharing of a pair of electrons between 2 covalently bonded atoms where one of the atoms supplies both electrons.


- Using dot and cross diagrams, draw the bonding in NH3BF3 and label the dative covalent bond. (2)

H3N->BF3
dative covalent donated by N to B

- main ions in Al2(SO4)3 (1)

Al3+ and SO4^ 2-

- Volume of PH3 gas produced = 360cm cubed
- 22.5 for another calculation
- bleaching ion ClO-


The questions are muddled up and the marks don't add up to 60 but couldn't think of anymore.

i have f322,f324,f325

i am confident with f322, f324 i like as it links with with f322.

f325... nightmare.

So you will have done all the chemistry exams this summer? If so same here. Have you already F324 or F325 and resitting?