CHEMISTRY - OXIDES, BASE, ETC!

bonkysleuth SG

Are oxides a sort of base???? Or ony basic oxides are considered base? Because there's this question where zinc oxide reacts with HCl to give zinc chloride and water. this is a neutralisation reaction isn't it?

the second question is,

an element , X , burns in oxygen to form an oxide that is soluble in water. the solution of this oxide has a pH greater than 7 . what is X?

A carbon

B copper

C Sodium

D sulphur.

Answer's sodium. don't really understand why. but i thought since the oxide dissolves in water, it should be an acidic one and thus a non-metallic element.

my friend says sodium reacts with oxygen to form sodium hydroxide? and this the pH is less than 7. i find this a little stranger and illogical. shouldn't it form sodium oxide?

Please help.thanks!

Darkness_hacker99 SG

Base
- A substance that reacts with acid to produce a salt and water. Metal oxides and hydroxides are bases. A soluble base is called an alkali

Alkali
- A substance that dissolves in water to produce hydroxide ions, OH-

Answering to your first question, YES, it's a neutralization reaction. The acid has been neutralized in the reaction, meaning its acidic properties has been destroyed.

Acid + base --> Salt and Water

Examples:

ZnO + 2HCl -- > ZnCl2 + H20

NaOH + HCl --> NaCl + H20

MgO + H2SO4 --> MgSO4 + H20

Question2. Glad that you think this way, but you didn't factor in the pH.
CO2 & SO2 dissolves in water to form an acidic solution; with means it has a pH value to less than 7.

Eliminate Carbon and Sulphur, left with Na and Cu.

Your friend is wrong. Sodium does not react with oxygen to from Sodium Hydroxide.

Here's the equation.
Sodium burns in oxygen to produce Sodium oxide.
4Na + O2 --> 2Na2O.

Sodium oxides dissolves in water to produce Sodium hydroxide.
Na2O + H2O --> 2NaOH

I rules out the possibility of Copper because to it's oxide were not able to dissolve in water. The placement of Cu in the reactivity series is low, and hence is generally less reactive.

starmoonsun SG

actually i think it shld b the following.

A base is a compound which when dissolved in water dissociates to produce hydroxide ions OH-. (metal oxides n hydroxides)

alkalis are bases that are soluble in water.

it is a form of neutralisation as the H+ ions from HCl will react with the OH- ions from the base to from H20

carbon and sulphur will dissolve to form acidic soln.

for copper, according the the reactivity series, is below hydrogen.hence, copper cannot displace hydrogen in HCl, thus there is no reaction

also, recall that all oxides and hydroxies are insoluble salts except oxides of sodium, potassium and ammonium (top of the reactivity series)

thus, copper is out too.

and the ans is sodium

gunner77 SG

if im not wrong

group 2 and 3 and transition metal are oxide