Question

3 Oxygen reacts with other elements to form oxides. Three examples are: calcium oxide, phosphorus pentoxide, and copper(II) oxide.
a Which of these is:
i an insoluble base?
ii a soluble base?
iii an acidic oxide?
b When the soluble base is dissolved in water, the solution changes the colour of litmus paper. What colour change will you see?
c Name the gas given off when the soluble base is heated with ammonium chloride.
d i Write a word equation for the reaction between the insoluble base and sulfuric acid.
ii What is this type of reaction called?
e Name another acidic oxide.

Answer 1

a)

(i) insoluble base = copper (II) oxide

(ii) soluble base = calcium oxide

(iii) phosphorus pent-oxide

b)

when soluble base ( means calcium oxide) dissolves in water then a chemical reaction takes place that gives a compound calcium hydroxide . which is basic in nature ,, hence it will turn red litmus blue.

c)

when soluble base ( calcium oxide ) is heated with ammonium chloride then a salt calcium chloride , water and ammonia gas is formed .

d)

(i)

copper(II) oxide + sulfuric acid

→→→→→→→ copper (II) sulfate + water vapour

(ii)

this is a type of double displacement reaction as well as can be said a neutralization reaction .

e)

Non metallic oxides are generally acidic in nature .

carbon is also a non metal

hence ,

Carbon dioxide is an acidic oxide.