OCR Chemistry F321 Exam. - [Next Tuesday[

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Hot Concentrated NaOH + Cl₂ is a key equation to know.

NaOH _(Aq) + Cl_{2 (G)} --> ?

Complete and if you can, balance (Unlikely to be needed, you probably only need the products). Add state symbols as well.

Reply 581

FreddieKeen

Original post by kj14

how does ca(oh)2 neutralise the acidic soil?

Because it is an alkali (it forms OH(-) ions in aqueous solution):
Ca(OH)2 (aq) ---> Ca(2+) (aq) + 2OH(-) (aq)

OH(-) neutralises acidic soil:
OH(-) (aq) + H(+) (aq) ---> H20 (l)

Water is (obviously) neutral.

(edited 11 years ago)

Reply 582

Dogfish44

OK, did ANYONE get the chloride question? I got 24.4 with magnesium, but I've hard everything inbetween.

Reply 583

PrincessMedic

How did you all find it?! I think the paper wasn't bad, but I ran out of time and made silly mistakes! :O

Reply 584

beckycat

Original post by Dogfish44

OK, did ANYONE get the chloride question? I got 24.4 with magnesium, but I've hard everything inbetween.

I got magnesium too :smile:

Reply 585

xe_nia

I got magnesium as well, but the paper was bleh.
What exactly did we need to write in the question about intermolecular forces in sulfur?

Reply 586

Dogfish44

I'm trying to remember how the marks were split up:

Q1 [23]
Q2 [9]
a) 1 Mark - Periodicity
b) 6 Mark - Essay Question :mad:

c) 2 Marks - Graph Ionisation energy increases, Atomic Radius decreases (Neither starts/ends at 0)
Q3 [12]
Q4 [16]

These sound right so far?

Reply 587

StephenDudge

I got Magnesium. But I had to somehow change the 0.06 moles to 0.03 for no reason to get it :/

Not sure on the bonding in the NH4CL, what was that?

Reply 588

eemooz

So how does everyone think it went?

Reply 589

Brad0440

Original post by Dogfish44

OK, did ANYONE get the chloride question? I got 24.4 with magnesium, but I've hard everything inbetween.

I got 12.2 somehow :s-smilie:

Reply 590

JoeLatics

Original post by StephenDudge

I got Magnesium. But I had to somehow change the 0.06 moles to 0.03 for no reason to get it :/

Not sure on the bonding in the NH4CL, what was that?

1:2 stoichiometry!!!

Pretty easy having done A2! :tongue:

Mg was right, btw.

Reply 591

eemooz

Original post by Dogfish44

I'm trying to remember how the marks were split up:

Q1 [23]
Q2 [9]
a) 1 Mark - Periodicity
b) 6 Mark - Essay Question :mad:

c) 2 Marks - Graph Ionisation energy increases, Atomic Radius decreases (Neither starts/ends at 0)
Q3 [12]
Q4 [16]

These sound right so far?

Yup, sounds right :smile:

Reply 592

xe_nia

yeah, because if you write an equation, it's 2AgNO3 + MCl2 = 2AgCl + stuff isn't it :smile:

Reply 593

eemooz

Original post by StephenDudge

I got Magnesium. But I had to somehow change the 0.06 moles to 0.03 for no reason to get it :/

Not sure on the bonding in the NH4CL, what was that?

The bonding in NH4CL WAS NH4+ and Cl-
The NH4+ had one dative covalent bond

Reply 594

NilabKebab

Youre not allowed to discuss till midnight people!
Other than that, hope all of you done well :smile:

Reply 595

StephenDudge

Original post by eemooz

The bonding in NH4CL WAS NH4+ and Cl-
The NH4+ had one dative covalent bond

So it wasn't that the N had 5 bonds. One being a dative covalent bond to an H?

(edited 11 years ago)

Reply 596

eemooz

Original post by xe_nia

I got magnesium as well, but the paper was bleh.
What exactly did we need to write in the question about intermolecular forces in sulfur?

For rmolecular forces I got giant covalent lattice so strong covalent bonds need to be broken for the sulphur to melt/boil.

Reply 597

eemooz

Original post by StephenDudge

So it wasn't that the N had 5 bonds. One being a covalent bond to an H?

Nope, nitrogen has five outer electrons, 3 of them are used in covalent bonds with hydrogen, the other two are used to make ONE dative covalent bond with hydrogen where nitrogen donates both electrons,

Reply 598

master y

Original post by JoeLatics

1:2 stoichiometry!!!

Pretty easy having done A2! :tongue:

Mg was right, btw.

I got 24.7... but said it was magnesium... would i lose a mark??

Reply 599

rajiv.dua07

Original post by eemooz

For rmolecular forces I got giant covalent lattice so strong covalent bonds need to be broken for the sulphur to melt/boil.

I think the OP is referring to why VDW forces are the only IM forces in sulphur. The reason is that because Sulphur is a non-polar molecule, it can only experience instantaneous dipole-induced dipole attractions (i.e. VDW forces)