Change Around Us

When carbon-di-oxide is passed through lime water
1. calcium hydroxide is formed
2. white precipitate of CaO is formed
3. lime water turns milky
4. colour of lime water disappears
When a magnesium ribbon is burnt in air, the ash formed is
1. black
2. white
3. yellow
4. pink
Rancidity can be prevented by
1. adding antioxidants
2. storinf food away from light
3. keeping food in refrigerator
4. all of these
The reaction of H2 gas with oxygen gas to form water is an example of
1. combination
2. redox reaction
3. exorthermic reaction
4. all of these
On immersing an iron nail in CuSO4 solution for few minutes, you will observe
1. no reaction takes place
2. the colors of solution fades away
3. the surface of iron nails acquire a black coating
4. the colour of solution changes to green
Chemically rust is
1. hydrated ferrous
2. only ferric oxide
3. hydrated ferric oxide
4. none of these
Both CO2 and H2 gases are
1. heavier than air
2. colourless
3. acidic in nature
4. soluble in water
Fatty foods become rancid due to the process of
1. oxidation
2. corrosion
3. reduction
4. hydrogenation
_ metal undergoes rusting.
1. tin
2. sodium
3. copper
4. iron
When a magnesium ribbon is burnt in air, the ash formed is
1. black
2. white
3. yellow
4. pink
Fatty foods become rancid due to the presence of
1. oxidation
2. corrosion
3. reduction
4. hydrogenation