What is the color of rusted iron (iron oxide)?
a) reddish brown
b) black
c) silvery white
d) golden
Metals only rust when they are exposed to…..
a) air
b) salt
c) acid
d) alkali
Which of the following suggestion/s you will apply to prevent a metal from rusting?
a) apply coating of another metal
b) don’t left metal in open air
c) painting and electroplating
d) all of these
Tarnishing of Silver:
When silver is exposed to sulfur-containing
gases in the air, it discolours and then darkens as it reacts with the gas to
form a surface layer of tarnish. This process is called tarnishing, as
explained below in The science of silver tarnish and its cause.
Silver
objects get a ……….coating over time when they are exposed to air.
a) yellow
b)
brown
c) black
d) red
Which of the following agent gradually tarnishes the silver articles?
a) carbon dioxide
b) carbon monoxide
c) nitrogen
d) hydrogen sulphide
