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Chemistry: Post your doubts here!

Casablanca

Casablanca

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How many isomers with the formula C5H10 have the structures that involve pi bonding?
A- 3
B- 4
C- 5
D- 6

shouldn't the answer be 2? But there is no option 2, so it can't be. What is the answer and why?

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The products obtained by cracking an alkane, X, are methane, ethene, and propene.

The mole fraction of ethene in the products is 0.5.

What is X?

A- C6H14
B- C8H18
C- C9H20
D- C11H24

How do you calculate this?
 
Goku

Goku

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Can you please explain to me why the Answer is C ? How do you go on about such questions? Please and thankyou!!
the propellent used in the solid rocket booster is a mixture of Al and compound X..Compound X contains Cl in an oxidation state of +7
which of the following could be compound X
A) NH4Cl b) NH4ClO3 C) NH4ClO4 D) N2H5Cl
 
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smartangel

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Sulfur dioxide, SO2, is added to wines to prevent oxidation of ethanol by air. To determine the
amount of SO2, a sample of wine is titrated with iodine, I2. In this reaction, one mole of SO2 is
oxidised by one mole of I2.
What is the change in oxidation number of sulfur in this reaction?
A +2 to +4 B +2 to +6 C +4 to +5 D +4 to +6
ans D. whats the equation for this rxn?
 
Casablanca

Casablanca

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Goku said:
Can you please explain to me why the Answer is C ? How do you go on about such questions? Please and thankyou!!
the propellent used in the solid rocket booster is a mixture of Al and compound X..Compound X contains Cl in an oxidation state of +7
which of the following could be compound X
A) NH4Cl b) NH4ClO3 C) NH4ClO4 D) N2H5Cl
Click to expand...

Oxidation no. of N is -3.
Oxidation no. of H is +1.
Oxidation no. of O is -2.
Sum of oxidation no.s in a compound must equal zero.

When you calculate it, C is the only option.

Because, look:

NH4ClO4 -> -3+4+x-8=0
-> 1+x-8=0
-> -7+x=0
->x=7
 
Student12

Student12

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Ashique said:
15-
sadcas-1.jpg



Question 23
You need to know the general formulas of the organic compounds listeed-
A- alcohols- CnH2n+1OH, hydrogen to carbon ratio- 4:1
B- Aldehydes- CnH2n+1CHO. hydrogen to carbon ratio- 2:1
C carboxylic acid, CnH2n+2COOH. hydrogen to carbon ratio- 2:1
D- Halogenoalkanes, CnH2n+1X, hydrogen to carbon ratio- 3:1

Greatest ratio shown by alcohols. Hence answer is A.

Question 25-
When ethanol refluxed with potassium dichormate, you'll get a carboxylic acid. Molar ratio remails 1:1. So moles of ethanol react was 2.76/46= 0.06 mol,
Since molar ratio is 1:1, 0.06 mol of ethanoic acid will also form, so mass of ethanoic acid formed= 0.01*61=3.66g
The yeild of product was 75%, so 75% of 3.66= 2.75, almost equal to 2,70, hence answer is C.
Click to expand...

Alright thanks :D
Though thought of making corrections..
- General formula of carboxylic acid is CnH2n +1 COOH
- the second sentence of Q25 is o.o6*61=3.66
 
M

Muhammad Asif

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nerdybookworm said:
ok sorry i posted the wrong link..now here help........paper 1 m/j 03 Q 2,4,8,10,16,20,27,28,30 & 39......


http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s03_qp_1.pdf
Click to expand...
Q2: see that one chain in residue has 2 double bonds while and 2 chains have single double bonds thus 4 doubl bonds in all....thus only 5 are hydrogenated.....1 double bond needs 1mol H2 so 5 needs 5mol H2

Q4:the highest difference in ionisation energies is 6 and 7th thus the element contain 6 electrons in outer shell thus group 6 that is C

Q8:the only change is in A....

Q10:the molar ratio of HI:I2:H2= 2:1:1 the change in HI is .26 so change in rest would be .26/2=.13......moles at equillibrium would be for H2=.07 and I2=.02 thus the only ans is C

Q16:chlorine disproportionate in conc hot NaOH forming NaClO3 where chlorine is +5(fact)

Q20:there are seven possible structures.....try to draw them

Q27=only chlorine----carbon bond can be broken to form a redical Cl....thus C is d answer as in the other options no Cl bond is broken

Q28=sorry:p

Q30=the answer is D as an additional C is added to Chain and an OH + acid group are made from the product hydrolysis....


q39=fehling test is positive thus the product is an aldehyde which can only be form from a primary alcohol which are shown in only 2 and 3
 
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smartangel

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Casablanca said:
Hmm, that sounds strange. Are you sure they all have a double bond though? Because it asks for ones with a double bond.
Click to expand...
yeah all of them have a double bond..cis trans, but 1 ene and but 2 ene...
anyone else who understands why the answer is 3?
 
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Muhammad Asif

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smartangel said:
yeah all of them have a double bond..cis trans, but 1 ene and but 2 ene...
anyone else who understands why the answer is 3?
Click to expand...
but-1-ene will only have cis no trans........becuse in both cases H will face H.....but-2-ene will have cis and trans thus the answer is C
 
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smartangel

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Muhammad Asif said:
but-1-ene will only have cis no trans........becuse in both cases H will face H.....but-2-ene will have cis and trans thus the answer is C
Click to expand...
no..what i meant was that the compound they"ve shown has cis trans isomers. other STRUCURAL isomers are but 1 ene and but 2 ene due to the different position of double bond.
 
T

TheMan123

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muneexa said:
Which organic molecules are planar other than ethene????
Click to expand...
There are many, to name all of them would be difficult. Just remember planar= either 2 bonding pairs(180) or 3 bonding pairs(120) or 2bonding pair with 1 lone pair(120)
 
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Muhammad Asif

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smartangel said:
no..what i meant was that the compound they"ve shown has cis trans isomers. other STRUCURAL isomers are but 1 ene and but 2 ene due to the different position of double bond.
Click to expand...
what?????????????????????????????no way?????how does the compound shown have cis-trans?????the methyl group are on same carbon atom not on different carbon atoms..........
 
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TheMan123

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when an alcohol is oxidised to a carbonyl, it is not considered a condensation reaction even though H2O is formed, can someone explain?
 
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