Hi, I have some questions about chemistry and hope I can get as much info as possible. I couldn't find information on google, nor in my 2 textbooks and I even went to the library and searched another textbook.. to no avail. Pleaes please help by answering any thing that you know.. its for my test tommorow!
1. Question of acid salts..
My textbooks say that sodium hydrogencarbonate is an acid salt... Does it mean that when you dissolve it in water, the pH is less than 7?
My chemistry teacher said ( some time ago ) that when a weak acid like carbonic acid, reacts with a strong alkali like sodium hydroxide, then the salt formed is alkaline... A chemistry website agrees with him.. "Salts made of the anion of a strong acid and the cation of a strong base will be neutral salts, that is, the water solution with this salt will have a pH of seven. (example - sodium chloride)
Salts made of the anion of a strong acid and the cation of a weak base will be acid salts, that is, the water solution with this salt will have a pH of less than seven. (example - ammonium chloride)
Salts made of the anion of a weak acid and a strong base will be an alkali salt. The pH of the solution will be over seven. (example - sodium bicarbonate)
It can be a bit more difficult to tell the pH of a salt solution if the salt is made of the anion of a weak acid and the cation of a weak base. Usually, the main determining factor is whether the weak acid is weaker than the weak base, but that is not always the case. For the purpose of the problems in the review section, you may say that the pH of a 'weak-weak' salt is indeterminate." from http://www.chemtutor.com/acid.htm#phst
However, my textbook says sodium hydrogencarbonate is ACID salt!! Is it that even tho its an acid salt, when dissolved in water it is alkaline??
2. Iron (III) Sulphate
I have done a titration with iron(III) sulphate and iron(II) sulphate ( which is colourless if I remember correctly? is it?? please confirm with me.... )
Ok I did this some time back so cannot remember clearly
But one thing I do remember clearly is that there is a kind of greenish tint to the solution when KMnO4 and FeSO4 is mixed.... before the endpoint ( which is pale pink ). What is this greenish tint about? The chemical equation on the right-hand-side has potassium sulphate, manganese sulphate, iron sulphate and water... I suspect the greenish tint is a combination of all these chemicals??
I would also like to clarify certain things...
What is the colour of iron(II)sulphate crystals?? ( i read from internet... its blue-green, true??? )
What is the colour of iron (III) sulphate solution and its crystals( I don't know and cant find any info... )
3. Test for nitrate
The textbook test for nitrate invovles
1. add dilute sodium hydroxide
2. add a bit of aluminium powder
3. if nitrate is present, ammonia gas is produced..
How do these chemicals react??? Does sodium hydroxide react with the nitrate?? ( I doubt so.. ) or does aluminium powder react with nitrate ( I dont know! )... Please teach me how this works cause in the textbook and internet theres nothing on it!!! Chemical equations will be helpful too thanks!
4. Aluminium Oxide
The layer of Al2O3 outside aluminium... it readily dissolves when Mercury (II) Chloride is rubbed aganst it... What's the chemistry behind this??? Cant be displacement
5. Hydrochloric acid and potassium permanganate...
Do they react??
Again, all these questions I ask here because there's no information on google so its a last resort... Please help... my chem common test is tommorow! ( eh.. its no really a big exam but i want to get better grades this time! )