Multiple choice questions (1 Viewer)

[abbadell]

Can someone please do these questions so i can check my answers
1 Which of the following 0.1 mol soltuions would have the highest pH?
(a) ammonia
(b) hydrobromic acid
(c)sodium hydroxide
(d)cardon dioxide

2 When pure ammonium chloride is dissolved in pure water at a temp of 25C, the pH of the resulting soltuion is less than 7. This is beacuse:
(a) Ammonium ions accept protons from water leaving OH ions in the soultion
(b) Cholride ions make the solution acidic
(c) Amminium ions combine with water molecules to give ammonium hydroxide
(d) Water molecules accept protons from ammonium ions, forming H30 ions

 

[airie]

I would think C is the answer for question 1, since B is an acid and D is acidic, but I don't know that much about ammonia Looking at question 2, it seems that A would be acidic too though And by elimination, D seems to be the most suitable answer for question 2

 

[insert-username]

Can someone please do these questions so i can check my answers
1 Which of the following 0.1 mol soltuions would have the highest pH?
(a) ammonia
(b) hydrobromic acid
(c)sodium hydroxide
(d)cardon dioxide

C - sodium hydroxide is the strongest base here and would have the highest pH

2 When pure ammonium chloride is dissolved in pure water at a temp of 25C, the pH of the resulting soltuion is less than 7. This is beacuse:
(a) Ammonium ions accept protons from water leaving OH ions in the soultion
(b) Cholride ions make the solution acidic
(c) Amminium ions combine with water molecules to give ammonium hydroxide
(d) Water molecules accept protons from ammonium ions, forming H30 ions

D would be my guess - all the other answers either raise the pH of the solution, or don't happen.


I_F

 

[lilchezza]

I was also thinking C for q 1, but didn't know much about ammonia either, wikipedia has cleared that up
"The ammonium ion can act as a very weak acid in the sense that it can protonate a stronger base using any one of its hydrogen ( H ) atoms and convert back to ammonia." So q 1 has to be C.
And I also think q 2 would be D, as from wikipedia (a) would be wrong as it would not accept protons, but donate them. And as insert username said, "the other answers either raise the pH of the solution, or don't happen."

 

[airie]

There you go abbadell, identical answers from us three

 

[jjames-hall]

yeh as said, ammonia can be a weak acid but has a greater tendancy to be a base, but since the question says that the result of disolving it in water results in a PH < 7 then it is logical to say it has formed an acid and therefore D is logical, as when acids disolve they form H30+ ions

and remember NaOH as an example of a very strong base, commonly known as caustic soda

 

[abbadell]

Thanks guys

 

[Riviet]

When an ion of a substance like a salt (that could be neutral, basic or acidic) reacts with water, this is known as hydrolysis. When ammonium reacts with water slightly (hence the equilibrium equation), the water acts as the base, and accepts a proton (hydrogen) from ammonium, to form ammonia and hydronium. It is the hydronium that causes the pH to be slighly below 7. Hope that helps.