Chemo P5 tips

[miss irfan]

in the experiment to investigate how solubility depends on temperature how do we actually change the temperature for different experiments? do we first dissolve a solid in known water at a particular temperature(lets say 60C) and note the temperate at which crystals form and then change the temperature to 80C and repeat the process?

 

[Paradoxical]

Best of luck guys! Insh'Allah we all have an easy paper. ^_^

 

[smzimran]

Best of luck guys! Insh'Allah we all have an easy paper. ^_^

Inshallah,
Aameen!

 

[hassam]

well for delta H sol.....it says dont accept mass of liquid + solid bt ony mass of liquid in the m in mcdelta T......i was taking mass of solution....nw why is dat

 

[hassam]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w07_qp_5.pdf
in question 1 he says control vriable shud be mass of hydroxide bt i think it shud be moles and not the masss!!!?......cos more the moles u have more will be heat evolved

 

[user]

thats easy.....delta y/delta x
cn smone tell me waht moles to divide by when calclating enthaloy change of neutralization

Assalamoalaikum wr wb!
well, according to the definition of enthalpy change of neutralization, it's so when ONE mole of water is formed ...right..so like the energy we found actually corresponds to the no. of moles of water produced by our experiment...a balance eqn and knowing which one is limiting will help u find this out.....now if Q be the energy for x moles of water, find out the enthalpy for 1 mol of water...

well for delta H sol.....it says dont accept mass of liquid + solid bt ony mass of liquid in the m in mcdelta T......i was taking mass of solution....nw why is dat

Note this point somewhere....when calculating the enthalpy changes, we do not consider the mass of ANY SOLIDS added. what we take is the VOLUME of solution, of which the temperature is raised. In that case remember, IF you're adding a 'solution' to another, rather than a solid, you'd take the total volume of the 2 solutions,....and that's cuz temp of the whole solution will be raised,right..!
^Make sure you know this...It's important.

 

[mybch]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_53.pdf

Q. no. 1 c :- How to ensure that none of the oxygen is lost ?
Generally, how do you prepare 'divided flasks' ? To prevent the loss of gas produced in the equation ?

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s07_er.pdf
1d vii.

did you get an answer for this?

 

[user]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_qp_5.pdf
in question 1 he says control vriable shud be mass of hydroxide bt i think it shud be moles and not the masss!!!?......cos more the moles u have more will be heat evolved

whether it's the mass or moles..it's the samething..?! moles = mass/Mr

 

[zenyatales]

did you get an answer for this?

this picture explains the divided flask quite clearly. but i m still not sure if its as okay to use a thistle funnel and a beaker, as to use a
divided flask for gas collection. :/

http://www.google.com.np/imgres?hl=...nw=78&start=0&ndsp=15&ved=1t:429,r:0,s:0,i:63

 

[rockchic]

How did P51 go for everyone? What did you guys get for the slope in Q2- proving Charle's Law??????

 

[angelicsuccubus]

I did p52... how was that?

 

[bestgirl]

for p51 gradient was 0.086 and yours?

 

[rockchic]

yay!!!!!!!!!! me toooo...... and what about the first question....the planning part. How did you do the question " calculate the molar concentration on one solution"?

 

[rockchic]

And also, what anomalous points did you get on the graph? I got :
Point 3: below the line
Point 8 (I think- or point 7- no... i think it's 8): above the line

 

[bestgirl]

for question 1 i didnt really know the planning...
anomalous were point 3 and the other was somewhere in the middle (i dont remember which one)
what did you write for the reasons?

 

[rockchic]

For 3: The point below the line: Temperature was measured prematurely, before complete expansion could take place
For 8: The point above the line: Gas was allowed to expand for more than 5 minutes - so over-expansion occurred.
It's kind of spooky that I got the exact same gradient- 0.086 ....
Did anyone else do the planning question????? Where have all the 51 people gone???

 

[mr_perfect]

i gave chem P52 xams . i flunked badly. i would probably score just 7 out of 30. can anyone tell me how much i need to score in P42 to get an A in Chemistry. I got A 82% in chem in AS.

 

[ziemah11]

For question 2, explanation in O/N 2010 ER is the best ever:

The ER states:

Two points about data tables are common every session. Firstly, candidates need to label each new column
used. These labels require three items – a written label, a correct unit and an expression to be used to
calculate the column data. All of these items are required for credit to be awarded (often the expression is
omitted). Secondly, the data needs to be correctly quoted, to either a specified number of decimal places or
significant figures. In this examination, the data requirement was for 3 significant figures. Usually, the table
head and data requirements are given below the table, so candidates should be advised to look there before
calculating any data.
In scaling the axes on a graph plot, candidates should always consider if the true origin (0,0) would be a
point on the line. If so, it should always be included in the scales since it would always be a reliable, correct
point. Two factors need to be taken into account when scaling the axes. The points need to be plotted
within at least half of each axis and the scale should be reasonable to facilitate accurate plotting. For
example data of 1, 2, 4 or 5 to 1 large square (of 10 small squares) would be reasonable but 3 or 6 or 7 to 1
large square (of 10 small squares) would not. Some candidates would benefit from practice in fitting a
reasonable scale into the grid first that uses at least half of each axis.
When referring to the reason for an anomalous result, it should be stressed to candidates that they
unambiguously define the point (e.g. Experiment 4) before stating a reason. This is vital when there is more
than one anomaly.

For tables:

Each column heading needs three things, a description (e.g. concentration of acid in water), a unit
(e.g. /mol dm-3) and an expression to calculate the data (e.g. B x 0.1/20) as required in the text
below the table.
Also below the table is stated a requirement for a specific number of significant figures or decimal
places. There is a general misunderstanding of the difference between significant figures, decimal
places and trailing zeros. In this case the requirement was for three significant figures. There was
a frequent misunderstanding of this requirement. For example, 0.0105 (3sig figs.) was given as
0.011 (3dp), even to the extent of seeing 0.0105 written but crossed out and replaced by 0.011
where, presumably, the candidate believes three decimal places is the same as three significant
figures. Also a calculated value of 0.05 needs to reported as 0.0500 if three significant figures are
required. Care needs to be taken with the reporting of data.
The two required columns involved a great deal of calculation. Each column required the
calculation of moles of sodium hydroxide, converting this into moles of succinic acid then a
concentration of acid. Only the more able candidates had any success here. Many managed two
parts of these calculations but usually not the 2:1 relationship between succinic acid and sodium
hydroxide. This may have been due to unfamiliarity with succinic acid or its formula. Quite a
significant minority labelled the columns “moles of sodium hydroxide” rather than concentration in
each solvent even though this was stated below the table.

For graph plotting:
The scaling of the axes seems to cause misjudgement in the minds of some candidates. There
seems to be a determination to cover the whole span of the grid regardless of the implications of
the axis scaling necessary to achieve that. An example of difficult scaling is 1 large square being
0.03. This would make each small square (1 mm) 0.003. This creates difficulties for the candidate
in correctly plotting data of the nature of 0.00552 so mis-plotting is often seen when such
inconvenient scales are chosen. Another example of difficult scaling was a 1 mm square being
0.00218 on the x-axis and 0.000223 on the y-axis. Such scales require the extensive use of a
calculator to adequately plot the data which in the very least may take some time. Some
candidates chose a scale for the acid concentration in water that did not accommodate all the
points giving the last point outside the grid. The scaling chosen must adequately cover the
available grid but the minimum requirement is for the plot to cover at least half of the grid in both
directions. So the candidates must make a compromise between scaling and grid coverage to use
at least half of the grid in both directions with a reasonable scale that can be easily used. Much
better scaling for the concentration in the water layer would have been 1 large square for 0.0125 or
0.02 mol dm-3 (depending on which axis) and for the concentration in the ether layer, 1 large square
for 0.001 mol dm-3.
Two more factors need to be considered in graph work. Firstly it is the independent variable that is
to be plotted on the x-axis and the dependent on the y-axis. Almost uniquely in this particular
question either variable could be plotted on either axis. Secondly the data/relationships should
always be examined to see if the origin (0,0) is a valid point. If so (as in this question) then the
scaling used must include the origin and any line drawn would include the origin since it would be a
definite point not subject to any experimental error as the other points may be.

A requirement for determining a slope is the use of construction lines on the plot to produce
co-ordinates for the slope calculation. Many candidates did not draw construction lines.

Hope all this helps with question 2

which paper 5 is this? paper 52 or 53 or others? thanks

 

[ziemah11]

this is NOTES (summary) of chem p5 i joined the thing together properly which i got from this forum especially from zeebujha. may these will help you.

 

[Varuna0911]

hello could you help me with june 2012 diagram part and planning for no 1 please ?