Advertisements
Advertisements
Question
Write equations for the reactions of calcium and potassium with water.
Solution
The reaction of calcium with water is exothermic, but the heat that evolved is not sufficient for the hydrogen to catch fire.
\[\ce{Ca_{(s)} + 2H2O_{(l)} -> Ca(OH)2_{(aq)} + H2_{(g)}}\]
Calcium starts floating because bubbles of hydrogen gas form and stick to the surface of the metal.
Potassium reacts violently with cold water, and its reaction is so violent and exothermic that the evolved hydrogen immediately catches fire.
\[\ce{2K_{(s)} + 2H2O_{(l)} -> 2KOH_{(aq)} + H2_{(g)}}\]
APPEARS IN
RELATED QUESTIONS
.................... liberated when acetic acid reacts with sodium metal.
(a) Hydrogen
(b) Chlorine
(c) Oxygen
(d) Nitrogen
A solution of CuSO4 in water is .................... in colour.
(a) Pink
(b) Blue
(c) Colourless
(d) Green
Write the electron-dot structures for sodium, oxygen and magnesium.
Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Explain the following reaction with the help of a balanced chemical equation:
Magnesium reacts with hot water.
Name two metals which form amphoteric oxides.
A copper coin is kept immersed in a solution of silver nitrate for some time. What will happen to the coin and the colour of the solution?
Complete and balance the following equation:
Cu (NO3)2 (aq) + Zn(s) →
What happens when calcium reacts with chlorine? Write an equation for the reaction which takes place
Arrange the following metals in order of their chemical reactivity, placing the most reactive metal first:
Magnesium, Copper, Iron, Sodium, Zinc, Lead, Calcium.
Which gas is produced when dilute hydrochloric acid is added to a reactive metal?
Write one reaction in which aluminium oxide behaves as a basic oxide and another in which it behaves as an acidic oxide.
Write the equation for the reaction of Zinc with dilute hydrochloric acid.
Name the products formed. Also indicate the physical states of all the substances involved.
Write the equation for the reaction of Iron with dilute hydrochloric acid.
Name the products formed. Also indicate the physical states of all the substances involved.
Name one metal more reactive and another less reactive than hydrogen.
The elements whose oxides can turn phenolphthalein solution pink are:
(a) Na and K
(b) K and C
(c) Na and S
(d) K and P
An element X reacts with hydrogen, when heated, to form a covalent hydride H2X. If H2X has a smell of rotten eggs, the element X is likely to be:
(a) carbon
(b) sulphur
(c) chlorine
(d) phosphorus
Which of the following pair of reactants can undergo a displacement reaction under appropriate conditions?
(a) MgSO4 + Fe
(b) ZnSO4 + Fe
(c) MgSO4 + Pb
(d) CuSO4 + Fe
What is the characteristic of the electronic configuration of noble gases?
Write a chemical equation to illustrate the use of aluminium for joining cracked railway lines.
