AS Chemistry P2 Prep.

[RGBM211]

The area under the graph (Boltzmann distribution) represents the amount of molecules which either possess enough energy to overcome the activation or not. The amount of molecules to the left of the activation energy is the amount that HAS the required activation energy.
Uhm... Hope that helps.

mmmm xtremly confused with the graph and how to explain it well yu this Ea barrier(activation energy) on the right hand side they shaded and it represents these fraction of molecules have energy equal to or greater then activation energy i dunt really understand boltzman distribution
few things i rembr ws smthing related to the reactant molecules colliding with each other in correct orrientation,molecules needs sufficent energy to form products etc etc....then the graph...its like as yu increase the temperature there is like less fraction of molecules having Ea equal to or greater...
p.s i dunt evn knw what i am saying

 

[littlecloud11]

hi.. I wanna ask a question abt organic chem..

Can alkane react with NaOH(aq) to form Alcohol??

No, they can't. It has to be a haloAlkane.

 

[RGBM211]

hi.. I wanna ask a question abt organic chem..

Can alkane react with NaOH(aq) to form Alcohol??

ermm all i know is that alkanes undergoes
1)combustion
2)free radical substitution
3)cracking

so id say nope

 

[littlecloud11]

mmmm xtremly confused with the graph and how to explain it well yu this Ea barrier(activation energy) on the right hand side they shaded and it represents these fraction of molecules have energy equal to or greater then activation energy i dunt really understand boltzman distribution
few things i rembr ws smthing related to the reactant molecules colliding with each other in correct orrientation,molecules needs sufficent energy to form products etc etc....then the graph...its like as yu increase the temperature there is like less fraction of molecules having Ea equal to or greater...
p.s i dunt evn knw what i am saying

Well the boltzman curve is an estimate of the energies possessed by molecules in a gas. Each molecule has it's own energy, some have more, some have a little less, but this is distributed About a mean; which corresponds to the peak of the boltzman curve. The no of molecules to the right of the Ea line have energy greater than the activation energy and can react. As you increase the temp. the peak of the curve shifts to the right and is lower than the peak at a lower temp. When the temp increases the area to the right of the Ea increases and so there is a greater no. of molecules now with energy more than Ea and so the reaction rate is faster.

 

[JulyMei]

ermm all i know is that alkanes undergoes
1)combustion
2)free radical substitution
3)cracking

so id say nope

yepp.. these are what i learnt too.. just wondering though. thanks!

 

[RGBM211]

Well the boltzman curve is an estimate of the energies possessed by molecules in a gas. Each molecule has it's own energy, some have more, some have a little less, but this is distributed About a mean; which corresponds to the peak of the boltzman curve. The no of molecules to the right of the Ea line have energy grater than the activation energy and can react. As you increase the temp. the peak of the curve shifts to the right and is lower than the peak at a lower temp. When the temp increases the area to the right of the Ea increases and so there is a greater no. of molecules now with energy more than Ea and so the reaction rate is faster.

so you mean the are on the right which is shaded will b more as we keep increasing the temperature ?

 

[AngelColdplay]

so you mean the are on the right which is shaded will b more as we keep increasing the temperature ?

Yup. You can see the area shaded is larger when the temperature is higher.

 

[RGBM211]

Yup. You can see the area shaded is larger when the temperature is higher.

oh great thanks for yur help guys lemme get some more doubts to be cleared

 

[littlecloud11]

so you mean the are on the right which is shaded will b more as we keep increasing the temperature ?

Exactly. Simultaneously the area to the left will be less. as you can see there is a larger area beneath the dotted line.

 

[RGBM211]

Exactly. Simultaneously the area to the left will be less. as you can see there is a larger area beneath the dotted line.

thanks got it

 

[RGBM211]

mmm
1)whats the advantage and disadavatages of fuel cells compared to combustion of hydrogen fuels ?

2)how reaction of esterification is carried out in a laboratory/school?

3)Eutrophication?

yea thats all

Anyone ?

 

[robotic94]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w04_qp_2.pdf

Q3 a iii

 

[DragonCub]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_2.pdf

Q3 a iii

Anode: oxidation, since chloride ion reacted to form chlorine gas, oxidation number rises from -1 to 0.
Cathode: reduction, since hydrogen ion reacted to form hydrogen gas, oxidation number drops from +1 to 0.
And just a small hint: oxidation always happens at the anode and reduction at the cathode.

 

[saudha]

whts the formula for enthalpy change?

 

[RGBM211]

whts the formula for enthalpy change?

sum of enthalpy of product- sum of enthalpy of reactant

 

[saudha]

why do you chnge the signs........of the reactant?

sum of enthalpy of product- sum of enthalpy of reactant

 

[saudha]

sum of enthalpy of product- sum of enthalpy of reactant

product - reactan or reactant - product....

 

[Saad (سعد)]

Thanks a lot littlecloud!

Just one question.

ii) use the formula Q= m*c* delT where, m is the mass of water in the solution. c is the specific heat capacity (4.18) of water and delT is the change in temp. [ for the mass of water, mass= density* volm. As the density of water is 1gcm^-3 the mass of water is the same as it's volume in the question]
so Q = 30* 4.18 * (26.2-21) = 652.08 J

Are we supposed to take the specific heat capacity of water as 4.18 or 4.2? o-o; I always thought its supposed to be taken to 1 decimal place...

 

[RGBM211]

product - reactan or reactant - product....

lol you can change signs if your doing the hesses law this is the general formula from the book

signs are changed depending on the direction if yu use hesses law(know its defination) that the total enthalphy change in a chemical reaction is independent of the route by which the chemical reaction takes place as long as the initial and final conditions are same

 

[Sana101]

"heat under reflux" should be more reliable. Small-molecule halogenoalkanes are usually in gaseous phase under room temperature. Reflux can ensure that the haloalkane is kept inside the container during the entire reaction.

aright thanks!