LOTS of misc. questions (1 Viewer)

[totallybord]

hi,
1) im really confused abt why some chemical equations have subscripts and some don't...is it in the syllabus?

2) and how do we know if some equation goes to completion so we don't ahve to put in the equilibrium sign?

3) in my textbook the jacaranda chemistry 2, in 6.1 question 5, why is the answer D? (to ppl who have the textbook)
ok im desperate so ill just type out the basic q. :
some guy tested W,X,Y,Z which are acid-base indicators on salt water, lemonade and washing soad and results are:
Salt Lemon Washing
W orange dark orange orange
X green pink violet
Y pirnk yellow yellow
Z yellow yellow orange

question is which best acts as an acid-base indicator and the answer is Z. now why would that be??
4) what does the pH range do or tell you? like the colour change of methyl orange is red to yellow (does that mean that it only has these 2 colours right?) and its pH range is 3.2 - 4.4... so what are u spose to get from it?

5) if 100mL of 0.104M nitric acid was mixed with 50mL 0.212M sulfuric acid. Calculate the conc of a) sulfate ions b) nitrate ions

6) it is required btwn 250mL and 2.0L of diluted solutions be prepared, having a conc of 0.315M. using only standard-sized volumetric glassware, what volumes of soultion A with a conc of 0.630M shld be diluted to what final volume to give 0.315M. More than one answer is possible.

7) if u had an equilibrium equation where it involved gases and the no. of moles on one side = no. of moles on other side and u increased the pressure, wld the equilirbium position be the same?

8) calculate the pH of a colution that contains 0.0020g of H(+) ion per L...what do u do?

sorry had so many qshopefully someone can answer themm!!thanks!!

 

[dan.121212]

1) do u mean states as in (g) (l) (aq) (s)? caus eif u do, make sure every chemical equation u write has states for all elements/compounds, i know some textbooks dont have them, but search the internet, look in another textbook do wateva u have to to find teh states - cause they in the HSC ur answer will be better if it has states

2) U dont have to put an eqauilibrium sign unless wat ur talking about has to do with it, for eg if u are talking about Le VChatelier's principle and teh CO2/H2O/H2CO3 equilibrium, u would cause its directly rrelated to it, but for eg if u are talking about teh dehydration of ethanol nah u dont cause its got nothin to do with equilibrium - so u sorta gottas judge whether its directly related to equilibrium topics, and if it is not (as it is in most cases) dont worry about the equilibrium sign

3) not sure about that Q - i dont have teh book so i dont know teh context surrounding it nor am i familiar with the acidity/basicity of those substances, but im sure it is to do with teh fact that probs lemonade and salt water have similar pH wheras washing soda is slightly different - not sure though

4)pH range is the range over which the indicator changes colour - so methyl orange, below 3.2 pH is red and above 4.4 is yellow, so thats what u get from it - teh pH range inbetween we cant account for

5)not sure what this Q Wants and its relevance to the syllabus

6) i ll skip those calculations

7) yes

8) pH = -log[H+] and 10^(-pH) = [H+]

therefore we need to use teh first equation
we need to convert the g/L into moles/L for concentartion

0.0020g/L = 0.001984 mol/L

pH = -log(0.001984) = 2.7

i think thats how u do it, not 100% sure

hope that helped