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thanks
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Chemistry: Post your doubts here!
- Thread starter XPFMember
- Start date
4c) as higher the temprature further the curve meaning Q and catalysed reaction has lowered Eathanks
5d) as only electron shielding effect is able to reduce ionisation energies sig and all the atoms have valance e in s shell and inc in neuclear charge will inc ionistion energy while group 1 elements have only one valnce e
10is c as only graphite T conducts electricity in solid state and MgO has higher boiling point than NaCl as stronger bonds
11c) as in a and b hydrogen bond needs to also be broken and in d well is endothermic hence c
14d) as its a prroperty
well for AS level its around this 50-60 for p2 27 for p1 and the remaining for p3
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its just one question
q1 molar enthalpy change of the reaction of pure sodium carbonate with hydrochloric acid is 49.5KJmol^-1
2.6g of washing soda was added to 50cm^3 of dilute hydrochloric acid in a plastic cup the temperature rose by 5C(specific heat capacity of the resulting solution=4.3) calculate the molar enthalpy change for the reaction of washing soda with dilute hcl
answer -43.8kjmol^-1
scourserlfc,
q1 molar enthalpy change of the reaction of pure sodium carbonate with hydrochloric acid is 49.5KJmol^-1
2.6g of washing soda was added to 50cm^3 of dilute hydrochloric acid in a plastic cup the temperature rose by 5C(specific heat capacity of the resulting solution=4.3) calculate the molar enthalpy change for the reaction of washing soda with dilute hcl
answer -43.8kjmol^-1
scourserlfc,
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please help me with no 4,510,11,14
and in 7, isnt the backward rate supposed to increase?
thanks in advance
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf
and in 7, isnt the backward rate supposed to increase?
thanks in advance
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf
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question no 4
bond breaking is endothermic which has a positive enthalpy change
bond forming is exothermic which has negative enthalpy change
R and Q is bond forming as u can see
p and s is bond breaking the magnitude of bond energy is given u can now find out which reaction is more negative
for question 7
u might know that a catalyst increases the rate of reaction of both endothermic and exothermic so does temperature .
the equilibrium is going to shift to backward reaction but that is not what the question demands. increasing temperature will increase the rate of exothermic and endothermic .
for question 10
ph closer to 7 means weak acid or weak alkali
student p makes a false statement maybe he was drunk . what is a difference between a strong alkali strong acid and a weak alkali weak acid .
strong acid or alkali is what that dissociates or ionizes completely . dissociation or ionization is the same thing here.
for question 14
astatine and iodide ion are insoluble in both aqueous and concentrated ammonia
bromide ion is soluble in concentrated ammonia but insoluble in dilute ammonia
chlorine is soluble in dilute ammonia
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- Messages
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top left box
CH3CH2OHCH3
top right box
CH3CH2COOH the other product is inorganic and is CO2
V= CH3CH2CHOHCH2OH
W= CH3CH2COCHO
4 =C because the curve (Boltzman) becomes more flatter and moves towards the right a little (increasing the molecular speeds while at the same time increasing the molecules with activation energy ! for the catalysed reaction just remember its definition that it provides an alternative route for the reaction,which has a lower activation energy !
5=D none of those options happen except last one more the inner shells are present more the inner electrons repel the outer ones away from nucleus and hence nucleus has almost no control over the outer ones
in 7 yes the backward yield will increase but building high pressure chambers capable of resisting more than 1MPa of pressure is expensive and so a compromise between the equilibrium concentration and economical value of the reaction has to be achieved otherwise the reaction will be very uneconomical
thats why answer is B10=C because as we all know ions never conduct electricity in solid form and also that mp and bp of MgO is bound to be bigger than NaCl because of its smaller ionic radius and more charge on its ions,then the third one is graphite due to high mp and bp but also because of its electrical conductivity in solid form a property which SiO2 doesnt have
11=answer is C,because in A and B the effect of other forces except hydrogen bonding is very less and hence they are mostly overcome,in D you are actually solidifying so u are actually helping in formation of Van der walls,in C you have CO2 being melted breaking VDW forces,(it has these forces and not dipol-dipole because CO2 shape is linear cancelling out effect of each O atom )
14=D because X is MgO and it has Mr of 40.3,is a white solid and is basic metal oxides are basic mostly but the solubility of MgO is very less the Mg(OH)2 formed in water is sparingly soluble and solubility increasing down the group due to factors which we study in A2
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thanks and also explain no 21,
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i wanted 2 know da explanation for V and W please?
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the answer is doubled because the equation says
"for decomposition of every 2 moles of NaHCO3,
1 mole of H2O and CO2
are produced.
so when you take Mr of one mole of H2O and CO2, you need to consider that there should have been 2 moles of NaHCO3
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how can we get october november 2012 papers?they arent on xtremepapers yet but are there any third party which have released them?
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i remember this was explained by a user last year in detail
go through the previous posts
by the way, here i go
consider the general formula of an aliphatic alkane chain
its CnH2n+2 (where n denotes the number of C/H present in the molecule)
so when there 20 carbon atoms present, there should have been [(2x20)+2=42] hydrogen atoms present.
but the number of hydrogen atoms present here are 28
which means theres a difference of 12 hydrogen atoms
Including an Oxygen atom (as the compound is an aldehyde) means you lose out 2 hydrogen atoms
12-2= 10
the difference now remaining is 10
Recall the basics
whenever there is a double bond you lose out two hydrgen atoms
i.e one from each of the carbon atoms that make double bond
therefore dividing 10 by 2 gives you 5
which should be the number of carbon=carbon double bonds
