chemistry questions..hope u all stop by :)

[AS-Girl]

hey guys
i just had few chemistry questions i couldn't solve! I would appreciate all the help I can get


1) How many ions per formula unit would you find if you dissolve (NH4)2 [Ce(NO3)6] in water?
a) 3    b) 9   C) 2    d)6


2)For baking soda, NaHCO3. What is the molar ratio of C to O? (i got confused between (b) and (d) )
a) 1:1        b) 3:1   c) 1:2     d) 1:3



3) lemon juice has a [H+] of 0.01 M. What is the [OH-]?
a) 1.0 x 10^-14 M
b)1.0 x 10^-7 M
c)1.0 x 10^- 12 M
d)1.0 x 10^2 M



That's all..Thanks in advance

[NotAbod]

2)For baking soda, NaHCO3. What is the molar ratio of C to O? (i got confused between (b) and (d) )
a) 1:1        b) 3:1   c) 1:2     d) 1:3

i am not an AS student but i think i can only help with question 2
ratio of C to O is 1 to 3, because each 3 oxygen atoms are bonded to 1 carbon atom, ( 1 C atom and 3 O atoms)
according to this, ratio C to O should be 1 Carbon to 3 Oxygen
Answer D
sorry i could'nt answer 1 and 3 cuz i didnt understand them ( i am an IGCSE student)
correct me please if i am wrong, i am not sure from the answer
~AboD

[Monopoly]

3) lemon juice has a [H+] of 0.01 M. What is the [OH-]?
a) 1.0 x 10^-14 M
b)1.0 x 10^-7 M
c)1.0 x 10^- 12 M
d)1.0 x 10^2 M

try using solubility product of water, K_w. K_w =  [H+][OH-]

 At 25^oC, K_w= 1.0x10^-14

thus [OH-]= k_w /[H+] = 1.0x10^-14/0.01

[AS-Girl]

hey abod
i'm not sure whether u compare O with C or C with O! lets get more opinions! (anyways thanks for ur try..appreciate it )


Thanks Monopoly..i totally understood the idea!!


one question left

[elemis]

hey abod
i'm not sure whether u compare O with C or C with O! lets get more opinions! (anyways thanks for ur try..appreciate it )


Thanks Monopoly..i totally understood the idea!!


one question left

The question says the molar ratio of C is to O..... pretty self-explanatory.

[AS-Girl]

got it! thanks

one more question :/

[AS-Girl]

1) How many ions per formula unit would you find if you dissolve (NH4)2 [Ce(NO3)6] in water?
a) 3    b) 9   C) 2    d)6

[AS-Girl]

If the pH of juice is 1.80, then the hydrogen ion concentration [H+] of the juice is:
a) 1.00 X10^-2 mole/liter
b)1.80 X 10^-2 mole/liter
c) 6.31 X10^-2 mole/liter
d) 1.58 X10^-2 mole/ liter


what i did is replaced all the values given  in the equation pH= -log[H+] and (d) gave me exactly 1.8


but surprisingly, the answer is (c) 

any ideas guys?

[Amii]

Are you sure the answer is C ? I get D too 

[AS-Girl]

Are you sure the answer is C ? I get D too 

yes..it's from an official paper 

[winnie101]

@ AS girl
i dont know why the replacing of concentrations isnt giving the right answer, but whenever you have to find conc. from pH or pOH you do the inverse of log which is the 10^x button on the calculator. so if you do 10^1.8 you get c.

[Amii]

@ AS girl
i dont know why the replacing of concentrations isnt giving the right answer, but whenever you have to find conc. from pH or pOH you do the inverse of log which is the 10^x button on the calculator. so if you do 10^1.8 you get c.

To calculate [H⁺] we use 10 ^-pH right?

And even if you don't include the - sign the answer comes 63.096 =  6.31X 10 ^-1 NOT 6.31 X 10 ^-2
 

[AS-Girl]

ok i have a similar question..
lets check if our way is right

If the pOH of a juice is 5.00, then the hydroxide ion concentration [H+] of the juice is:
a) 1.00 X10 ^(-9) mole/liter
b) 1.00 X10 ^(+5) mole/liter
c) 1.00 X10 ^(+9) mole/liter
d) 1.00 X10 ^(-5) mole/liter

[Amii]

then the hydroxide ion concentration [H+] of the juice is

Hydroxide ion concentration or hydrogen ion concentration ?

[OH-] would be 10^-5 =1 X 10 ^-5 mol/dm3

Thus [H+] =  1 X 10^-14
                   --------
                   1 X 10^-5

=1X10^-9 mol/dm3

[NotAbod]

Hydroxide ion concentration or hydrogen ion concentration ?

[OH-] would be 10^-5 =1 X 10 ^-5 mol/dm3

Thus [H+] =  1 X 10^-14
                   --------
                   1 X 10^-5

=1X10^-9 mol/dm3

Genius!!
i donno wat are u guys talking about! i am still an igcse newbie