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 [Chemistry] Chemistry Question

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withoutwax
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PostSubject: [Chemistry] Chemistry Question   [Chemistry] Chemistry Question Icon_minitimeMon Aug 04, 2008 10:00 pm

An impure sample of zinc weighting 50.0g reacts with 129mL of HCL (35.0% w/w). If the density of the HCL solution is 1.18g/cm3, calculate:

(a) the molarity of the HCL solution used in the reaction.

(b) the percentage of zinc in the impure sample



The density of 10.5 molal NAOH solution is 1.33g/cm3 at 20 celsius. Calculate,

(a) mole fraction of H2O

(b) molarity of CH3OH

(c) Molality of CH3OH
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withoutwax
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withoutwax

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PostSubject: Re: [Chemistry] Chemistry Question   [Chemistry] Chemistry Question Icon_minitimeMon Aug 04, 2008 10:01 pm

2NO + O2 ---> 2NO2 H<0
Draw an energy diagram to show the change in energy when No reacts with O2 to form NO2. Indicate clearly on your diagram the activation energy of each step in the mechanism.
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Admin
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PostSubject: Re: [Chemistry] Chemistry Question   [Chemistry] Chemistry Question Icon_minitimeWed Aug 06, 2008 1:57 am

No ppl reply geh? LOL
I am here to give some support........ What a Face lol!
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withoutwax
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withoutwax

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PostSubject: Re: [Chemistry] Chemistry Question   [Chemistry] Chemistry Question Icon_minitimeFri Aug 22, 2008 9:31 pm

X + Y -> Z

The above reaction is first order with respect to X and zero with respect to Y. Initial Conc. of X: 1.50 mol dm^-3
Initial Conc. of Y: 2.00 mol dm^-3
Initial rate of reaction: 6.70 X 10^-5 mol dm^-3 s^-1

What is the rate of reaction after one hour??

*post the answer pls~~
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mia

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PostSubject: Re: [Chemistry] Chemistry Question   [Chemistry] Chemistry Question Icon_minitimeSat Aug 23, 2008 12:28 am

affraid
are you testing us....?

Seriously, I did try.... Sad
but I dunno how to do..... Where did you get the questions??
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withoutwax
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PostSubject: Re: [Chemistry] Chemistry Question   [Chemistry] Chemistry Question Icon_minitimeSat Aug 23, 2008 1:09 pm

from a friend..net friend
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withoutwax
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PostSubject: Re: [Chemistry] Chemistry Question   [Chemistry] Chemistry Question Icon_minitimeSat Aug 23, 2008 5:24 pm

calculate the rate constant,
use the equation ln A = -kt + ln Ao , get final conc. of X, and
(Initial conc of X - final conc of X)/ 3600s

Ro =k x Ao
Rf =k x Af
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withoutwax
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PostSubject: Re: [Chemistry] Chemistry Question   [Chemistry] Chemistry Question Icon_minitimeTue Sep 16, 2008 8:09 pm

Right here is another interesting question!!

What is the mass of potassium hydroxide ,KOH that must be added to 250 cm^3 of 0.10 moldm^-3 hydrofluoric acid , HF in order to obtain a solution with pH 3.3 ?
[relative atomis mass , H=1 ; O=16 ; K=39 ; Ka HF = 6.8x10^-4 ]

(gimme the working pls..coz honestly i really dunno how to do~~)
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withoutwax
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PostSubject: Re: [Chemistry] Chemistry Question   [Chemistry] Chemistry Question Icon_minitimeMon Sep 22, 2008 10:08 pm

The equilibrium constant for the reaction

N2 (g) + 3H2 (g) --> 2 NH3 (g) is 4.0 x 10^-3 atm^-2 at 600 degree celcius. What is the pressure required to obtain a mixture containing 15% by volume of ammonia if the reaction starts with hydrogen and nitrogen in the molar ratio of 3:1?

A 7.4
B 8.9
C 10.1
D 13.2
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