module 20a paper 3

8/8/2019 Module 20A Paper 3

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TUISYEN IBNU SINA CHEMISTRY MODULE 20PAPER 3

Question 1An experiment is carried out to determine the end point of a neutralisation process. 50.00 cm3 ofaqueous potassium hydroxide 0.1 mol dm-3 is titrated against hydrochloric acid with an unknownconcentration using phenolphthalein as an indicator.The titration is repeated twice. Figure 1 shows the results of the experiment.

Titration Set 1 2 3

Initial BuretteReading

cm3 cm3 cm3

Final Burette

Reading

cm3 cm3 cm3

Figure 1

(a) State two observations that you could obtain during the experiment.

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1. .....

2. .....

(b) Record the burette readings in the spaces provided in Figure 1.

(c) Construct a table and record the initial burette readings, final burette readings and

volume of hydrochloric acid needed for each titration set.

(d) (i) What is the average volume of hydrochloric acid used in the experiment?

(ii) The chemical equation for the reaction is:

KOH + HCl KCl + H2O

Determine the concentration of hydrochloric acid used.

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(e) The experiment is repeated using sulphuric acid to replace hydrochloric acid.It was found that the volume of sulphuric acid required is half the volume ofhydrochloric acid used. State the inference of this observation.

..

...

(f) Potassium chloride which is produced in this experiment is an example of a solublesalt. Classify the following substances into soluble and insoluble salt.

Substances

Sodium sulphate Lead(II) iodide Barium sulphate

Magnesium nitrate Zinc carbonate Silver chloride

(g) Figure 2 shows three test tubes containing potassium hydroxide solution withdifferent concentrations and pH values.

Test tube 1 2 3

Concentration

0.1 mol dm-3

potassium hydroxide0.01mol dm-3

potassium hydroxide0.001 mol dm-3potassium hydroxide

pH value 13 12 11

Figure 2

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(i) Based from Figure 2give the operational definition for the pH value of an alkali.

.

..

(ii) Predict the pH value if the concentration of potassium hydroxide solution is 0.0001 mol dm -3

.............

..

(iii) As the concentration of the potassium hydroxide solution changes, the pH valuealso changes. Explain why.

................................

(iv) Complete the table below based on the experiment to identify the variables and show howthe variables are controlled.

Manipulated variables :

Action to be taken :

Responding variables :


How the variable responds? :

Fixed variables :


(v) State the hypothesis for this experiment.

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............

..

Question 2An experiment was conducted to find out the effect of temperature on the rate of reaction.50 cm3 of sodium thiosulphate solution 0.05 mol dm-3 at 30 oC was put into a 250 cm3 conicalflask. Then the conical flask was placed on an X sign on a piece of white paper.10 cm3 of hydrochloric acid 1.0 mol dm-3 was added to the sodium thiosulphate solution andshaken. At the same time, the stop watch was started. The stop watch was stopped as soon asthe X sign was no longer visible.The same steps of the experiment were repeated for sodium thiosulphate solution which washeated to35 oC, 40 oC, 45 oC, 50 oC,

Figure 2shows the readings of the stop watch for each of the reactions at differenttemperatures.

Figure 2

(a)Record the time for each reaction in the spaces provided in Figure 2.

(b) Construct a table and record temperature, time and for this experiment.

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time

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(c) (i) Draw a graph of temperature against on the graph paper.

(ii) Based on the graph in (c) (i), state the relationship between the rate of reaction andtemperature.

..

(d) Predict the time taken as soon as the sign X to be no longer visible if thisis repeated at 55 oC.

(e) State the variables involved in this experiment.

Manipulated variables :



Responding variables :



Fixed variables :


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(f) State the hypothesis for the experiment.

...

...

(g) From the above experiment, the student found a relationship between temperature andrate of reaction. The same situation can be applied in our daily lives, for example, keepingfood that is easily spoilt in the refrigerator.

Using your knowledge of chemistry, state the relationship between temperature andthe rate at which food turns bad.

.

.

Question 3An experiment is carried out to investigate the effect of concentration of ions on the selectivedischarge of ions at the electrodes.The setup of apparatus of the experiment are shown in Figure 4.

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Carbon electrodes

(Anode)

Carbon electrodes

(Cathode)

Copper(II)

chloride, CuCl2solution

Battery Switch

Figure 4


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The experiment is carried out by using copper(II) chloride solutions of 2.0 mol dm -3 and0.001 mol dm-3. The gas collected at anode is tested with damp blue litmus paper andglowing wooden splinter

(a) Complete the Table 2 by stating the observations and related inferences in the experiment.

Electrolyte Observations at anode

Copper(II) chloride, CuCl2solution of 2.0 mol dm-3

(i) Damp blue litmus paper:

________________________________________________

(ii) Glowing wooden splinter:

________________________________________________

________________________________________________

Copper(II) chloride, CuCl2solution of 0.001 mol dm-3

(i) Damp blue litmus paper:

________________________________________________

(ii) Glowing wooden splinter:

________________________________________________

________________________________________________

Table 2

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Damp blue litmus

paper

Glowing wooden

splinter

Figure 3


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(b) State the colour change of copper(II) chloride solution when experiment is carried out.

.

.

(c) Complete Table 3 based on the experiment.

Name of variables Action to be taken

(i) Manipulated variable:

_________________________________

_________________________________

(i) The way to manipulate variable:

__________________________________________________________________

(ii) Responding variable:

_________________________________

_________________________________

_________________________________

(ii) What to observe in the respondingvariable:

_________________________________

_________________________________

_________________________________

(iii) Fixed variable:_________________________________

_________________________________

_________________________________

(iii) The way to maintain the fixed variable:_________________________________

__________________________________

__________________________________

Table 3

(d) State one hypothesis for the experiment.

.

.

(e) Classify all the ions that exist in copper(II) chloride into cations and anions.

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Question 4

Equal volume of water is heated in two different copper container. Container 1is heated by using alcohol X while container 2 is heated by using alcohol Y.

It was discovered that the mass of alcohol X needed to boil the water is morecompared to alcohol Y.

Plan a laboratory experiment to compare the heat of combustion between alcohol X and Ybased on the above situation.

Your planning should include the following aspects:

(a) Problem statement

(b) All the variables

(c) Statement of hypothesis

(d) List of substances and apparatus

(e) Procedure of the experiment

(f) Tabulation of data

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module 20a paper 3

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