Question

13. Write balanced equations and give your observations when
the following metals react :
(i) Sodium with cold water
(ii) Calcium with cold water
(iii) Magnesium with boiling water
(iv) Magnesium with steam.​

Answer 1

Answer:

(1)

When sodium is dropped in cold water, it reacts explosively and burns with a golden yellow flame. The reaction is exothermic and vigourus. It form sodium hydroxide with the liberation of hydrogen gas.

Answer 2

Answer:

i)$2Na_{(s)}+2H_2O$   ⟶ $2NaOH_{(ag)}$+ $H_{2(g)}$ ↑

ii) $Ca_{(s)}+2H_2O$ ⟶ $CaOH_2{(ag)}$+ $H_{2(g)}$ ↑

iii)$MgO_{(s)} + H_2O(l)$ ⟶ $Mg(OH)_{2(aq)}$

iv)$Mg_{(s)} + H_2O_{(g)}$  ⟶ $MgO_{(s)} + H_{2(g)}$

Almost forgot the observation:

i)When sodium is dropped in cold water, it reacts explosively and burns with a golden yellow flame. The reaction is exothermic and vigorous. It form sodium hydroxide with the liberation of hydrogen gas.

ii)Calcium, for example, reacts fairly vigorously with cold water in an exothermic reaction. Bubbles of hydrogen gas are given off, and a white precipitate (of calcium hydroxide) is formed, together with an alkaline solution (also of calcium hydroxide - calcium hydroxide is slightly soluble).

iii)Magnesium reacts with hot water much faster to produce magnesium hydroxide and hydrogen gas. Magnesium hydroxide is insoluble in water and is slightly basic, which reacts with the universal indicator, turning the solution blue/green or with phenolphthalein to turn the solution pink.

iv)Magnesium burns in steam to produce white magnesium oxide and hydrogen gas. Very clean magnesium ribbon has a very slight reaction with cold water. After several minutes, some bubbles of hydrogen form on its surface, and the coil of magnesium ribbon usually floats to the surface.