Which indicator would best distinguish between a solution with a ph of 3.5 and a solution with a ph of 5.5?
(1) bromthymol blue (3) litmus
(2) bromcresol green (4) thymol blue

The pH range of given indicators are

i) bromothymol blue : 6 (yellow) to  7.6 (blue) : so it cannot be used for the given condition

ii) litmus : it senses the change between acid and base. blue litmus turns red in acidic medium (from basic or neutral) however here both the solutions are acidic so we cannot use it

iii) bromocresol green : the pH range is 3.8-5.4. Below 3.8 it is yellow and above 5.4 it is blue

thus we can use it for two solutions as

a) in solution of pH = 3.5 it will show yellow colour

b) in solution of pH =5.5 it will show blue colour

hence answer is Bromocresol green

iv) thymol blue: pH rang is 6.0 - 7.6, so cannot be used

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.