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Chemistry: Post your doubts here!

asadalam

asadalam

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nehaoscar said:
View attachment 54801
Why not C?
Is there a trick or some solution is solving these questions?
Like the electronegativity values are not in the data booklet so any tips on how to calculate these sort of questions to find the largest or smallest overall dipole?
Click to expand...
Because the Cl cancel out some of the net dipole caused by O.Similar in the case of CCl4 So3 etc where there are E-ve elements but no net dipole
 
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Tasneem_m98

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Please help ! O/N 2011 p11 question 33

The following statements are all true.
Which of these can be explained, at least in part, by reference to hydrogen bonding?
1 At 0°C ice floats on water.
2 The boiling point of propan-2-ol is 82°C. The boiling point of propanone is 56°C.
3 At 20°C propanal and propanone mix completely.

The answer is B (1 and 2 only are correct).
But i don't understand why cant 3 be correct. Dont propanal and propanone mix due to hydrogen bonding??
Thank you in advance!
 
asadalam

asadalam

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Tasneem_m98 said:
Please help ! O/N 2011 p11 question 33

The following statements are all true.
Which of these can be explained, at least in part, by reference to hydrogen bonding?
1 At 0°C ice floats on water.
2 The boiling point of propan-2-ol is 82°C. The boiling point of propanone is 56°C.
3 At 20°C propanal and propanone mix completely.

The answer is B (1 and 2 only are correct).
But i don't understand why cant 3 be correct. Dont propanal and propanone mix due to hydrogen bonding??
Thank you in advance!
Click to expand...
No as in propanal the H atom is not bonded to O atom so there will be no H-bonding if you look closely.H bonding requires H to be bonded with a highly electronegative atom like O,but in both cases O is bonded to C not H.
 
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Studydayandnight

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shazmina said:
First find the number of moles of K2Cr2O7
n = Vc
13.1*10^-3 *0.100 =1.31*10^-3 moles

As we know the mole ratio of Fe2+ to Cr2O7 2– we can cross multiply and find the number of moles of Fe2+ that have reacted with 1.31*10^-3 moles of Cr2O7 2–, which is equal to 7.86*10^-3 Moles
The Mr of Fe is 55.8g, so then multiply 7.86*10^-3 Moles of Fe2+ with it Mr to get the mass of iron that have reacted with K2Cr2O7 which is equal to 0.439

And then finally find the percentage by mass , 0.439/1*100 = 43.9%

Make sure you round off all the values to an appropriate significant figure when writing and remember to carry the Answers in your calculator for an accurate calculation :)
Click to expand...

Thank you!!
 
princess Anu

princess Anu

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qwertypoiu said:
Oxidation state of sulfur in S2O3 2- = +2
If u reduce 4 moles of chlorine from 0 to -1, the sulfur will gain +4.
Only D has oxidation state of +6.
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Isn't the thiosulphate ion (S2O3) donating 8 electrons in changing the state of 8 Cl atoms from O to -1? :s
 
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