Sarahisme

well i didn't see how this worked really, but anyways

The {H+}of neutral water (pH=7) is 1E-7. This HCl is a really weak solution (1E-8) of a strong acid, so you add the [H+] together (it's called the 5% rule and is used for weak acid solutions when the contribution of [H+] from the water is more than 5% of the [H+] from the acid), so in this case [H+]=1E-7+1E-8=1.1E-7. And pH=-log(1.1E-7)=6.96 This is a very weak acid solution.

my answers booklet says that its a bit less than 7 (~6.98)

hey i can't figure this question out... "What is the pH of the 1.0x10^-8 M HCL?" could i please have some help? Smile Thanks Sarah

*in my precious post

so was what i said correct? or way off track? :S

so your saying that you could "move" the right hydrogen that is going into the page, so that it will point downwards, and so this would now look like it is 'mirroring' the left hand bit, hence making it meso ??

also how in world is this meso?! aghhh stress...!!

oh and while were on this topic, could you please please please (i have test tomorrow) explain how these bonds come to Z ? Thanks

are you sure? because my answers booklet says that they are the same

i can't see how these two molcules are the same....??

oops nevermind, i just can't add up to 12. *shame*

would any chemistry wizz's be able to help me out with this problem...? i just don't see why the formal charge on the sulphur atom is zero, i thought i would be +3. Thanks Sarah

? i am not quite understanding, sorry

here it is...

hang on a sec and i'll upload a pic of problem in which this "cancelling" (or looks like cancelling to me) happens....

hey could someone please give me a bit of help with this big O notation bussiness, it makes not much sense to me, (mainly in terms of calucating limit sof indeterminate form, and how the big O's cancel etc.) anyways any help or pointers to a good website that explains the stuff would be great! Thanks Guys and Gals Sarah

yeah thats what i did for part a) but my answer was abit strange i thought ? :S

for a) i get ~5400km

hey could i please get some help or preferably answers to this question... i will post my answers but i don't know how long it will take me to figure them out...anyways heres the question: A geosynchronous satellite is one which maintains a fixed position above the earths surface, ie its orbital period has duration 24 hours. a) At what height above the Earth’s surface do you have to position a satellite so that it is in a geosynchronous orbit? (8 marks) b) Write down an expression for the energy required to position a satellite of mass m a distance d above the Earth’s surface. (6 marks) The space shuttle lifts a 500kg satellite to an orbit that is 1000 km above the Earth’s surface. c) How much more energy is required to position this satellite in a geosynchronous orbit? thanks guys Sarah

ok yeah ,well 85% and 60% is good i suppose, so thanks yep thanks everyone

hmm..interesting can anyone give me a link to a good site that explains this basic bit of organic chemistry? thanks Sarah

but i think it was fairly strong

dunno only used 6 drops of H2SO4

catalyst, ummm H2SO4 and acetic anhydride