Could someone give me some practice chemistry questions?

Watch
Announcements
This discussion is closed.
#1
E.g. on titration calculations and identifying salts?
E.g. you give me a situation such as, heat a compound X, a lilac flame is produced therefore it is a potassium compound, but I have to give the answer.
0
15 years ago
#2
Um I don't know if this is what you're looking for, but here you go:

Sulphamic acid reacts with sodium hydroxide according to the following equation:
NH2S03H + NaOH ---> NH2SO3Na + H20
A standard solution of sulphamic acid was made by dissolving 5.210g of the acid in water and making the volume up to exactly 250cm3 with more water

a) Calculate the number of moles of acid used and the molarity of the acid solution.

b) In a titration, 22.6cm3 of this acid solution were required to neutralise 25.0cm3 of sodium hydroxide solution. Calculate the molarity of the sodium hydroxide solution.
0
15 years ago
#3
(Original post by Widowmaker)
E.g. on titration calculations and identifying salts?
E.g. you give me a situation such as, heat a compound X, a lilac flame is produced therefore it is a potassium compound, but I have to give the answer.
What level / Exam board?
0
#4
(Original post by BarelyLegal)
Um I don't know if this is what you're looking for, but here you go:

Sulphamic acid reacts with sodium hydroxide according to the following equation:
NH2S03H + NaOH ---> NH2SO3Na + H20
A standard solution of sulphamic acid was made by dissolving 5.210g of the acid in water and making the volume up to exactly 250cm3 with more water

a) Calculate the number of moles of acid used and the molarity of the acid solution.

b) In a titration, 22.6cm3 of this acid solution were required to neutralise 25.0cm3 of sodium hydroxide solution. Calculate the molarity of the sodium hydroxide solution.
a) NH2S03H
5.210 grams
Molar mass = 97

No of moles = 5.210/97 = 0.0537 moles
=> 5.210/97 = (250*C)/1000
=> 5.210/97 = 0.25C
C = (4*5.210)/97 = 0.215 moldm^-3

b)
NH2S03H
V = 22.6cm3 = 0.0226dm^3
C = 0.215 moldm^-3

NaOH
V = 25.0cm3 = 0.025dm3
C = ?

At the equivalence point, the number of moles are equal.

no of moles of sulphamic acid = 0.0226*0.215 = 4.859*10^-3
=> no of moles of NaOH = 4.859*10^-3

4.859*10^-3 = 0.025C
C = 0.194moldm^-3
0
#5
(Original post by TakemetoAvalon)
What level / Exam board?
edexcel AS
0
#6
(Original post by Widowmaker)
a) NH2S03H
5.210 grams
Molar mass = 97

No of moles = 5.210/97 = 0.0537 moles
=> 5.210/97 = (250*C)/1000
=> 5.210/97 = 0.25C
C = (4*5.210)/97 = 0.215 moldm^-3

b)
NH2S03H
V = 22.6cm3 = 0.0226dm^3
C = 0.215 moldm^-3

NaOH
V = 25.0cm3 = 0.025dm3
C = ?

At the equivalence point, the number of moles are equal.

no of moles of sulphamic acid = 0.0226*0.215 = 4.859*10^-3
=> no of moles of NaOH = 4.859*10^-3

4.859*10^-3 = 0.025C
C = 0.194moldm^-3
Can someone check if this is correct? Question is above.
0
15 years ago
#7
(Original post by Widowmaker)
Can someone check if this is correct? Question is above.
Yes it is correct as far as I can see.
0
#8
(Original post by oxymoron)
Yes it is correct as far as I can see.
that's good, thankyou.
Do you know anything about the edexcel AS Chemistry practical?
0
15 years ago
#9
(Original post by Widowmaker)
that's good, thankyou.
Do you know anything about the edexcel AS Chemistry practical?
Did you do enthalpy change practice? Something like measure the temperature before and after the reaction ... then draw a graph, from it you can calculate the enthalpy change?
0
15 years ago
#10
Describe the effect of a nitro-substituent on directing the site of reaction in the electrophilic substitution of an aromatic compound (e.g. benzene). Rationalise that effect by considering charge stabilisation.
0
#11
(Original post by BCHL85)
Did you do enthalpy change practice? Something like measure the temperature before and after the reaction ... then draw a graph, from it you can calculate the enthalpy change?
yeah I can do those experiments no probs. my teacher put a notice up in the lab saying that one experiment is a titration, (probably sodium hydroxide and an acid and methyl orange as an indicator) and the other is identifying salts.
2 hours for each practical, but i'm just swotting up on these types of practicals, common mistakes and calculations.

If there are only two practicals, will there be a planning element to these practicals at all?
0
15 years ago
#12
(Original post by ChemistBoy)
Describe the effect of a nitro-substituent on directing the site of reaction in the electrophilic substitution of an aromatic compound (e.g. benzene). Rationalise that effect by considering charge stabilisation.
Sure those aren't A2 problems? I never covered substitution is Higher...
0
#13
(Original post by ChemistBoy)
Describe the effect of a nitro-substituent on directing the site of reaction in the electrophilic substitution of an aromatic compound (e.g. benzene). Rationalise that effect by considering charge stabilisation.
read what I am typing, I am not doing that!
0
15 years ago
#14
(Original post by Widowmaker)
read what I am typing, I am not doing that!
widomaker, where did you get your avatar? I think i might steal it I made mine! I can't be bothered searching...
0
15 years ago
#15
(Original post by TakemetoAvalon)
widomaker, where did you get your avatar? I think i might steal it I made mine! I can't be bothered searching...
lol, I saw it quite familiar, is it in "spirited away" ?
0
15 years ago
#16
(Original post by BCHL85)
lol, I saw it quite familiar, is it in "spirited away" ?
Yeah, that's right.. the little dudes made out of soot!
0
#17
Can anyone give me any other practice questions?
ask me questions about safety, titrations and precautions to be taken, and identifying salts (edexcel) mainly groups 1,2 and 7.
0
15 years ago
#18
(Original post by Widowmaker)
Can anyone give me any other practice questions?
ask me questions about safety, titrations and precautions to be taken, and identifying salts (edexcel) mainly groups 1,2 and 7.
I'm sure you'll be fine in your practical exam. If the question is indentifying a compound , you should remember how to realise all the substance, cations, anions, gas, solid ... either by colour or smell, litmus paper, flame test, ect. Did you have the summary note of these?
0
#19
(Original post by BCHL85)
I'm sure you'll be fine in your practical exam. If the question is indentifying a compound , you should remember how to realise all the substance, cations, anions, gas, solid ... either by colour or smell, litmus paper, flame test, ect. Did you have the summary note of these?
yeah, i've made my own revision notes. I printed off the spec last week.
0
#20
I'm trying to see if there are any more titration precautions.
Here is my list.

Ensure that solution does not go above 0 in burette.
Check for bubbles in burette and above burette tap.
Ensure tap is closed when pouring solution into burette.
Funnel must be removed from burette after solution has been poured in.
Volumetric flask must be shaken 10-15 times to ensure solution is mixed.

I'm sure there are more obvious ones. Can you think of any?
0
X
new posts
Back
to top
Latest
My Feed

Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Poll

Join the discussion

How will you be receiving your results?

Going into school to pick them up (195)
33.28%
Receiving them online / by email (291)
49.66%
I still don't know (100)
17.06%