gcse chemistry question help?

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username3743764
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#1
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#1
I was wondering if anyone could help me with this question?

A scientist produces zinc iodide (ZnI2).
This is the method used.

1. Weigh 0.500 g of iodine.
2. Dissolve the iodine in ethanol.
3. Add an excess of zinc.
4. Stir the mixture until there is no further change.
5. Filter off the excess zinc.
6. Evaporate off the ethanol.

0 7 . 1 )Ethanol is flammable.
Suggest how the scientist could carry out Step 6 safely. [1 mark]

0 7 . 2 )Explain why the scientist adds excess zinc rather than excess iodine
[3 marks]

0 7 . 3) Calculate the minimum mass of zinc that needs to be added to 0.500 g of iodine so that the iodine fully reacts. [3 marks]

The equation for the reaction is:
Zn + I2  ZnI2

Relative atomic masses (Ar): Zn = 65 I = 127
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SmartMemoryGirl!
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#2
Report 4 years ago
#2
(Original post by laiba786)
I was wondering if anyone could help me with this question?

A scientist produces zinc iodide (ZnI2).
This is the method used.

1. Weigh 0.500 g of iodine.
2. Dissolve the iodine in ethanol.
3. Add an excess of zinc.
4. Stir the mixture until there is no further change.
5. Filter off the excess zinc.
6. Evaporate off the ethanol.

0 7 . 1 )Ethanol is flammable.
Suggest how the scientist could carry out Step 6 safely. [1 mark]

0 7 . 2 )Explain why the scientist adds excess zinc rather than excess iodine
[3 marks]

0 7 . 3) Calculate the minimum mass of zinc that needs to be added to 0.500 g of iodine so that the iodine fully reacts. [3 marks]

The equation for the reaction is:
Zn + I2  ZnI2

Relative atomic masses (Ar): Zn = 65 I = 127
7.3) 0.5/127=0.00393700787 mol
0.00393700787*65= 0.25590551155g
I think not sure.



You can search for any mathematical expression, using functions such as: sin, cos, sqrt, etc. You can find a complete list of functions h
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username3743764
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#3
Report Thread starter 4 years ago
#3
(Original post by SmartMemoryGirl!)
7.3) 0.5/127=0.00393700787 mol
0.00393700787*65= 0.25590551155g
I think not sure.



You can search for any mathematical expression, using functions such as: sin, cos, sqrt, etc. You can find a complete list of functions h
tysm x
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bean101
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#4
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#4
1) use a water bath (no flame)
2) because zinc is solid therefore can be filtered out easily using filter paper, when iodine can’t
3) can’t be bothered working it out think someone has already answered it hahaha 😂😂😂
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username3723410
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#5
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#5
1) I would say using a heatproof mat, wearing goggles, etc
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bean101
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#6
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#6
(Original post by somebrick)
1) I would say using a heatproof mat, wearing goggles, etc
This way it would still pose a safety hazard though because although safety precautions are being made, it’s still not exactly safe. From my knowledge, 9/10 of the time with questions concerning alcohols and flames, the answer scheme will specify that waterbaths are a safer alternative )
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username3723410
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#7
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#7
(Original post by bean101)
This way it would still pose a safety hazard though because although safety precautions are being made, it’s still not exactly safe. From my knowledge, 9/10 of the time with questions concerning alcohols and flames, the answer scheme will specify that waterbaths are a safer alternative )
oo thanks, guess yours is the best answer. will remember this in the exams
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creepia
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#8
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#8
Hi, you forgot to multiply iodine's molar mass by two as it is a diatomic molecule.So it would be:0.5/127(2)= 1.97 ×10^-31:1 ratio of moles - (1.97×10^-3)*65=0.128 g There's another way you could do it too:Find out the percentage of iodine in zinc iodide by formula/molar mass -- 127(2)/65 2(127)*100=79.62% Let x be the total mass of zinc iodide= 79.62/100=0.5/x79.62x=50X=50/79.62=0.63gYou then subtract the mass of iodine from the total mass of zinc iodide to get the minimum mass of zinc.0.63g-0.5g=0.128g
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Nate.tredson
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#9
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#9
Where did you get the question
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todd_03
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#10
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#10
this is almost correct. Iodine comes as a pair (I2) so you would need to multiply the mr by 2. instead of 127, it is 254:0.5/254 = 0.00197mol0.00197 * 65 = 0.128hope this is helpful
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pv6048
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#11
Report 1 year ago
#11
(Original post by username3743764)
I was wondering if anyone could help me with this question?

A scientist produces zinc iodide (ZnI2).
This is the method used.

1. Weigh 0.500 g of iodine.
2. Dissolve the iodine in ethanol.
3. Add an excess of zinc.
4. Stir the mixture until there is no further change.
5. Filter off the excess zinc.
6. Evaporate off the ethanol.

0 7 . 1 )Ethanol is flammable.
Suggest how the scientist could carry out Step 6 safely. [1 mark]
- use a water bath
or
- evaporate the ethanol at room temperature
0 7 . 2 )Explain why the scientist adds excess zinc rather than excess iodine
[3 marks]

0 7 . 3) Calculate the minimum mass of zinc that needs to be added to 0.500 g of iodine so that the iodine fully reacts. [3 marks]

The equation for the reaction is:
Zn + I2  ZnI2

Relative atomic masses (Ar): Zn = 65 I = 127
(Original post by username3723410)
1) I would say using a heatproof mat, wearing goggles, etc
I would have thought you were right, but that you are actually stating the precautions
Here is saying state a SAFETY METHOD
which can be
- heat the ethanol in a water bath
- or keep the ethanol at room temperature when heating
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