for chem... does concentration affect acidity of acid? yes or no, please explain thanks.
for SS.. for the rise of venice, what are the social factors? list them out please. thanks
acidity is measured by the concentration of H+ or OH- in the solution so the concentration of an acid or alkali will affect acidity.
SS idk, too long din take liao xD
hmm... still a bit blur about the acidity, since water has H+ and OH- ions... but water exist as molecule in liquid form right? but when something dissolve in water, the water molucule will change to ion?
urmm for SS i got one more question...
just now i ask, for the rise of venice, what are the social factors? list them out please..
then now i got another question... is the industrial devlopment counted as social or economic? i am refferring to the trade-related industry like the shipbuilding industry located at Arsenal to prevent noise...
also the new industrise creating more jobs to attract ppl... the innovative practises like giro and double bookkeeping.... are these all social or econimic or what factors?
ah ok it goes by a balance...if the solution has more H+ ions then it is acidic, if it has more OH- ions then it is basic...
water exists as a molecule in liquid but as ions in AQUEOUS state...
hmm.. that is the thing i dunno... how water exist as aqueous state?
cuz from what i know or learnt or believe... a thing is aqueous when dissolved in water... but how water dissolve in water.. dun make sense to me... thanks a lot tho!
Originally posted by ItchyArmpit:hmm.. that is the thing i dunno... how water exist as aqueous state?
cuz from what i know or learnt or believe... a thing is aqueous when dissolved in water... but how water dissolve in water.. dun make sense to me... thanks a lot tho!
lol i thought that too...
theres only one social factor in the rise of venice i know of: Attitude towards trade
if you are using the purple-coloured social studies book, there's a point "Nation-building" you may want take a look at, in page 121. They say the people developed a sense of belonging, were determined in harsh conditions by maintaining social cohesion, etc.
Originally posted by qdtimes2:lol i thought that too...
theres only one social factor in the rise of venice i know of: Attitude towards trade
if you are using the purple-coloured social studies book, there's a point "Nation-building" you may want take a look at, in page 121. They say the people developed a sense of belonging, were determined in harsh conditions by maintaining social cohesion, etc.
hmm thanks a lot!! btw double-entry bookkeeping and giro-banking... they counted as social factors? sounds like tho.. it is a service, but i dun think it is political... economic, maybe... or maybe social... this is so confusing! SS is so hard to understand lol
ok i went googling.. after some search i came upon this website.. http://www.newton.dep.anl.gov/askasci/chem03/chem03575.htm
to summarize this up and to answer my own question...
to start off... we know that by weak acid, it means that only a small percentage of H+ is given off by the acid when dissolved in water...
and strong acid... it means that almost all or all of the H+ ions has been given off in the water...
pH value is actually a calculation of number of H+ or OH- ... and we know that the lower the pH value, the more acidic the solution is, and higher the more alkaline.
if we link all these up, we can explain by saying that when we have a solution of pH value 4, it can mean that
it is a little concentrated solution of weak acid
or
or something that is of very very very very dilute STRONG acid..
but still.. the water thing, i still cant understand... it is suppose to exist as molecule in liquid form, but in electrolysis, we put it as ions... so does that mean water only exist as ion in liquid form? cuz we can also electrolyse water by itself..
pls clear my doubt and correct me if i have any wrong conception... Thanks!
Originally posted by ItchyArmpit:ok i went googling.. after some search i came upon this website.. http://www.newton.dep.anl.gov/askasci/chem03/chem03575.htm
to summarize this up and to answer my own question...
to start off... we know that by weak acid, it means that only a small percentage of H+ is given off by the acid when dissolved in water...
and strong acid... it means that almost all or all of the H+ ions has been given off in the water...
pH value is actually a calculation of number of H+ or OH- ... and we know that the lower the pH value, the more acidic the solution is, and higher the more alkaline.
if we link all these up, we can explain by saying that when we have a solution of pH value 4, it can mean that
it is a little concentrated solution of weak acid
or
or something that is of very very very very dilute STRONG acid..
but still.. the water thing, i still cant understand... it is suppose to exist as molecule in liquid form, but in electrolysis, we put it as ions... so does that mean water only exist as ion in liquid form? cuz we can also electrolyse water by itself..
pls clear my doubt and correct me if i have any wrong conception... Thanks!
coz in electrolysis the charges cause the molecules to change into ionic forms to gain or lose the electron...if u writing formulae and the water u know is end up in ionic form then u must put as (aq)...if is ionic form must b aqueuos cannot put (l)
o ic... so water can never be in aqueous state unless during electrolysis?
Originally posted by ItchyArmpit:o ic... so water can never be in aqueous state unless during electrolysis?
erm...that idk lol...thats all i can rmb la so far xD quite long din touch chem liao must understand lol
Haha! thanks a lot man.
from my knowledge(yeah im taking chem this year too),
concentration does not affect acidity of the acid.
you can have a very dilute HCl but the ph will still be 2.
vice versa you can have a strong ethanoic acid but the ph will still be 5/6.
the part about water molecules im not too sure,
but pure water cannot be an electrolyte as it exists as simple discrete molecules.
however with just one drop of acid/alkali,
the acid dissociates in the water when it dissolves and the water molecules exists as ions(which can be used in electrolysis)
correct me if im wrong, thanks! off to study Ss nao.
water alone exists as neutral molecules. so it cant be used as an electrolyte.
Originally posted by xstryker:from my knowledge(yeah im taking chem this year too),
concentration does not affect acidity of the acid.
you can have a very dilute HCl but the ph will still be 2.
vice versa you can have a strong ethanoic acid but the ph will still be 5/6.
the part about water molecules im not too sure,
but pure water cannot be an electrolyte as it exists as simple discrete molecules.
however with just one drop of acid/alkali,
the acid dissociates in the water when it dissolves and the water molecules exists as ions(which can be used in electrolysis)
correct me if im wrong, thanks! off to study Ss nao.
urmm see the link i posted in my earlier posts...
anyway.. thanks all for replying.. i learnt a lot :)
haha .
concentrated ethanoic acid need not be strong
dilute HCL need not be week .
Originally posted by yiha093:haha .
concentrated ethanoic acid need not be strong
dilute HCL need not be week .
but can an extremely dilute HCl acid have the same pH value as an extremely concentrated ethanoic acid?
no.
conc is amount of mol per dm3
ph value is ion dissociation.
ok thanks!
urmm another question...
1. In distillation
a) where does the water enter and leave the condenser?
b) why do we not let it flow int he opposite direction?
2.
a)Where is the bulb of the thermometer placed?
b) what temperature does it show?
please see if my answer is correct or wrong... and for 1b) i totally dont know.
1a) Water enter from the bottom of the condender and leave from the top of the condenser. (is it right to say bottom and top of condender? it feels wierd to say that)
1b) i totally dont know
2a) The bulb of the thermometer is placed above the solution being distillated and near the entrance of the condenser.
2b) It shows the temperature of the boiliing point of the substance in the mixture which has the lowest boiling point, followed by the next higher boiling point and continue to the highest boiling point of the substance in the mixture.
i feel that all my answers sounds wierd. please give me ur model answer, and please elaborate and explain more on 1b). thanks!
another question.
A student says that the perfume does not diffuse but is carried around by the air currents. What can you do to check?
edit: nvm i know le.. for those curious, it is to drop a few drops of liquid bromine in a gas jar. The bromine evaporates to fill the gas jar with reddish-brown vapour. Place another gas jar full of air above the gas jar filled with bromine vapour. Remove the lid that is separating the two gas jar, u will see the reddish-brown vapour filling up the whole 2 gas jar even though it is denser than air.
(disclaimer: i saw this answer in my textbook)
another chem question.
when a reaction occurs, and the temperature decreases, is it an endothermic or exothermic reaction?
my answer is endothermic, because take in heat energy.. correct?
temperature of what decreases?if temperature of surrounding decreases, yes its endothermic, if temperature of solution decreases then different liao...
Originally posted by darkhour:temperature of what decreases?if temperature of surrounding decreases, yes its endothermic, if temperature of solution decreases then different liao...
but technically it is not possible to measure the tmep of 'reacting particles'
u can only measure temp of soln and surrounding ( both are same)
i dun understand wth u talking about 1b)
its freaking vague.
the temperature will affect the surrounding too... so it is about the same.. so i guess it is endothermic right?
1b) the question is actually asking why we do not let the water enter from the top of the condenser and leave from the bottom of the condenser?