Physics, Chemistry and Biology: Post your doubts here!

[Phoenix Blood]

How to get about?

 

[Phoenix Blood]

Why can't it be conc. NaCl solution plainly too?

 

[exploded diper]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s11_qp_21.pdf
Q10 allllll parrttts

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s11_qp_21.pdf
1200*2=2400,2400*2=4800.......as the half life is 15 hours so the original countrate must have been doubled for 15 hours and thn doubled agn for the other 15 hours to make 30hours.............as it asked vat the rate was (before) the start of the experiment.......
Q11 ciii

 

[exploded diper]

Why can't it be conc. NaCl solution plainly too?

if it was conc thn hydrogen would be released at the electrode instead of sodium(metal)........question had asked to liberate the metal........

 

[exploded diper]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s10_qp_41.pdf
Q4 a)i and a)ii ???

between like charges....instead of poles....there u go hope u understan vat it means..........

 

[Phoenix Blood]

if it was conc thn hydrogen would be released at the electrode instead of sodium(metal)........question had asked to liberate the metal........

A concentrated solution ... does it mean that it contains water?

 

[exploded diper]

A concentrated solution ... does it mean that it contains water?

yes...concenterated and dilute are aqueous solutions.....

 

[exploded diper]

explain with the help of a diagram sumone plz....

 

[Phoenix Blood]

These two...? eureka!

 

[Phoenix Blood]

Help me out.
eureka!

 

[pyaparus]

What are ionic equations?

 

[exploded diper]

Help me out.
eureka!

20 volume of hydrocarbon + 150vol. o2 = 100 vol. co2 + (20 vol) h20
so 2hydc--> 10 co2
1:5...whic mean there r fice carbons in the hydrocarbon....
15*2=30..o2--->10*2(C)o2+10(h2)o
30-20=10>>(h2)o
so 2hydc-->10(h2)
so 1hydc--->5(h2)...tht equals to 10h
so hydrocarbon contains c5h10....
so the equation is 2c5h10+15O2--->10co2+10h2o

 

[Phoenix Blood]

20 volume of hydrocarbon + 150vol. o2 = 100 vol. co2 + (20 vol) h20
so 2hydc--> 10 co2
1:5...whic mean there r fice carbons in the hydrocarbon....
15*2=30..o2--->10*2(C)o2+10(h2)o
30-20=10>>(h2)o
so 2hydc-->10(h2)
so 1hydc--->5(h2)...tht equals to 10h
so hydrocarbon contains c5h10....
so the equation is 2c5h10+15O2--->10co2+10h2o

Thanks!

 

[eureka!]

These two...? eureka!

Sorry! Didn't see this until after the exam. Anyway, I guess you've to simply describe it the way you'd describe SiO2. Giant macromolecule. Tetrahedral, each Ge atom covalently bonded to 4 O (1Ge : 4O), and 1 O atom bonded to 2 Ge atoms (1O : 2Ge). Very strong covalent bonds.

 

[eureka!]

0625_s13_qp_12 Question 33?

Yeah, I mucked up in that one too. Dunno why that's the answer, sorry about it!

 

[eureka!]

What are ionic equations?

Equations in which you've gotta mention the oxidation numbers and exclude all spectator ions.
Eg., in the displacement of tin ions by magnesium atoms.
Mg + Sn2+ -> Mg2+ + Sn

 

[Phoenix Blood]

Sorry! Didn't see this until after the exam. Anyway, I guess you've to simply describe it the way you'd describe SiO2. Giant macromolecule. Tetrahedral, each Ge atom covalently bonded to 4 O (1Ge : 4O), and 1 O atom bonded to 2 Ge atoms (1O : 2Ge). Very strong covalent bonds.

You know what? - this idiocy had come in the paper I'd seen the answer in the MS, but i dunno... Do we have to KNOW this or DERIVE it?

 

[exploded diper]

0625_s13_qp_12 Question 33?

since x and y are parallel there resistance is less.........so when y is removed the resistance across x increeases..and so does the voltage...as x and z are arranged in series so voltage across z decreases so it becomes less brighter......brightness depends on voltage

 

[exploded diper]

You know what? - this idiocy had come in the paper I'd seen the answer in the MS, but i dunno... Do we have to KNOW this or DERIVE it?

derive it......

 

[princess sofia]

cn any1 plz ans thx