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Physics, Chemistry and Biology: Post your doubts here!

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suhaib05

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Chemistry doubt: "Deduce the formula of the alkene which has a relative molecular mass of 168. Show your working."

How can you solve this algebraically rather than using trial and error?
 
thats_me

thats_me

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suhaib05 said:
Chemistry doubt: "Deduce the formula of the alkene which has a relative molecular mass of 168. Show your working."

How can you solve this algebraically rather than using trial and error?
Click to expand...
general formula for alkene Cn H2n
so (12n+2n)=168
14n=168
n=168/14=12
 
sma786

sma786

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thats_me said:
3b: One of the uses of zinc is galvanising ,In this method the metal (zinc) protects steel objects from rusting to do this the zinc coating rusts instead of steel... Here Zinc( being more reactive )is oxidised in preference to iron by loosing its electrons and forming ions ...
4b: you need to learn this Oxidising agent + potassium iodide : colour changes from colourless to brown
Click to expand...
thanksssss
 
NIM

NIM

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1)- Sulfur dioxide is made by spraying molten sulfur into air. The sulfur ignites and sulfur dioxide is formed.
Suggest why molten sulfur is used in the form of a fi ne spray???
2) Antimony, Sb, is an element in Group V.
The main ore of antimony is its sulfi de. The extraction of antimony is similar to that of zinc.
Describe how each of these changes in the extraction of antimony is carried out.
(i) antimony sulfi de to antimony oxide
(ii) antimony oxide to antimony

3) Scandium fluoride is an ionic compound.
The valency of scandium is three. Draw a diagram which shows the formula of the compound, the charges on the ions and the arrangement of the valency electrons around the negative ion.
Use x to represent an electron from a scandium atom.
Use o to represent an electron from a fl uorine atom.
Guys really need help!!!
 
Z

za Shadow

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thats_me

thats_me

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NIM said:
1)- Sulfur dioxide is made by spraying molten sulfur into air. The sulfur ignites and sulfur dioxide is formed.
Suggest why molten sulfur is used in the form of a fi ne spray???
2) Antimony, Sb, is an element in Group V.
The main ore of antimony is its sulfi de. The extraction of antimony is similar to that of zinc.
Describe how each of these changes in the extraction of antimony is carried out.
(i) antimony sulfi de to antimony oxide
(ii) antimony oxide to antimony

3) Scandium fluoride is an ionic compound.
The valency of scandium is three. Draw a diagram which shows the formula of the compound, the charges on the ions and the arrangement of the valency electrons around the negative ion.
Use x to represent an electron from a scandium atom.
Use o to represent an electron from a fl uorine atom.
Guys really need help!!!
Click to expand...
Here..
1: As it increases the surface area & more particles are being exposed so faster reaction.
2i :By supplying hot oxygen for roasting of antimony sulfide
ii :By reducing antimony oxide with carbon
Lol may be the worse drawing ever :p
 

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xxxt

xxxt

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the formula is T3(Po4)2 because from the graph u can see dat 8 cm3 of phosphate solutions makes max height of precipitate..phosphates valancy is always -3...for that of t u hv to use the mole ratio after writing the equation which should guide you
 
xxxt

xxxt

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za Shadow said:
plzzzzzzzzzz help
q 3 d ii)
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w11_qp_33.pdf
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w11_ms_33.pdf

my answer was: "reducing agent.....as it is gain of hydrogen and decrease in negative charge"
but WHYYY is it wrong why is the correct answer "base. Proton acceptor"
Mine is also correct :(
HELLLLPPPPP PLZZZZZZ I NEED U GUYS :cry:
Click to expand...
it is a proton acceptor because it takes hydrogen ion from sulfuric acid...and a base by definition is the one that accspts protons from proton donators i.e acids.
 
xxxt

xxxt

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E

EpicLol

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E

EpicLol

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xxxt said:
4b(ii) oxidation is loss of electrons and iodide ions will loss the electrons they took in order to become ions
4b(iii)because ozone makes the iodide to loss their electrons
7a(ii)during crakinga long chain alkane is broken to a long chain alkene and a short chain alkane soo...
it will be
C10H22->C4H8+C6H4
Click to expand...

I agree with the top two but not the last one....it would be C4H8 and C6H12 and H2 .....
 
areebaization

areebaization

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I have a doubt guys! Since almost all metals are cations and reduction happens at cathode can we say that metals get reduced? OR the substance that gets disposed off (in the form of gas or solid precipitate at the bottom of the beaker) at the electrodes is generally reduced? :S
 
E

EpicLol

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areebaization said:
I have a doubt guys! Since almost all metals are cations and reduction happens at cathode can we say that metals get reduced? OR the substance that gets disposed off (in the form of gas or solid precipitate at the bottom of the beaker) at the electrodes is generally reduced? :S
Click to expand...

I have the same question.....it came in like one of the past papers I did like ages ago......
 
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