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Chemistry -
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Spot-ify Offline
Pariah

Posts: 752
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Post: #1
Chemistry -

I have a couple lot of question that need answering; I could send you some money via paypal - need it doing pronto though.

Hidden stuff:
1) Jack was told to prepare the soluble sale, magnesium chloride. He added magnesium power to dilute hydrochloric acid in a beaker, until the reaction stopped. The diagram shows what he did.
[Image: zuovnd.png]
(1A)Describe the safety precautions Jack should take when doing this.
This reaction is very fast.
(1B) Suggest ways in which Jack could slow down the reaction.

(1C) Describe how Jack can obtain pure, dry magnesium chloride crystals from his mixture. You may draw a diagram if this helps.

2) Sandeep was told to make the insoluble sale lead iodide from lead nitrate solution and potassium iodide solution.
(2A) Describe how Sandeep can obtain pure, dry lead iodide.

3) Kirsty investigated the reaction between sodium hydroxide solution and hydrochloric acid. This neutralisation reaction produces heat.

Kirsty put 23cm3 of dilute hydrochloric acid into a polystyrene beaker.
She added 10cm3 of sodium hydroxide solution to the acid.
She recorded the maximum temperature of the mixture.
As soon as the mixture reached the maximum temperature, she added a further 10cm3 of sodium hydroxide and again recorded the maximum temperature. She repeated the experiment until a total of 60cm3 of sodium hydroxide solution had been added. Her results are shown in the table.
[Image: 20fqdf5.png]

(3A) Draw a graph of temperature against volume of sodium hydroxide solution added on the grid.


(3B) Use scientific principles to suggest reasons for the shape of the graph.
(3C) Use the graph you drew to suggest the highest temperature reached by the reaction mixture
(3D) Suggest how Kirsty could improve the reliability of her data.

Kirsty looked at her graph and came to this conclusion. "My graph shows that neutralisation was complete when exactly 20cm3 of sodium hydroxide had been added"
4(A) Explain whether you agree, or disagree, with Kirsty's conclusion and give scientific reasons to support your answer.

This forms a % of my GCSE so yeah I'll pay about £5/$8. Need it done soon though

I used to be "The circus" as I forgot my login, but then hey-ho I remembered it.
12-10-2009 02:33 AM
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FindTheLight Offline
Revolutionary

Posts: 148
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Post: #2
Re: Chemistry -

I can do a few. [Edit: I've done a few more/rewritten some]

1)a) Safety goggles to protect the eyes during the experiement.
Tie all loose clothing back.
Add the Magnesium under eye-level.

b) Temperature of the reaction (do it at a lower temp)
Decrease the concentration of the acid
Decrease the surface area size of the magnesium.

c)Evaporate the solution.

3)c) 31*C

d) Repeat her test and take an average
Compare her results with someone else who has carried out the same experiment.

4)a) Disagree: Eventhough the maximum temperature begins to decrease there is no measurement of pH. The misture still continues to react after 20cm3 has been added.




Hope any of that helps. I can only answer simple stuff and I'm never 100% certain so only go with these if you feel right.

Hope some others can give you better answers. Good luck!

[Image: 110.jpg]
12-10-2009 06:22 AM
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