Advertisements
Advertisements
प्रश्न
Write equations for the reactions of calcium and potassium with water.
Advertisements
उत्तर
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
संबंधित प्रश्न
.................... 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
Food cans are coated with tin and not with zinc because ______.
The reaction of an iron nail with copper sulphate solution is ........... reaction.
(a) Combination
(b) Displacement
(c) Double displacement
(d) Decomposition
Name the metal which has been placed at the bottom of the reactivity series.
How would you show that silver is chemically less reactive than copper?
Complete and balance the following equation:
Na2O + H2O →
What type of oxides are formed when non-metals react with oxygen? Explain with an example.
Name two metals which can, however, liberate hydrogen gas from very dilute nitric acid.
A copper plate was dipped in AgNO3 solution. After certain time, silver from the solution was deposited on the copper plate. State the reason why it happened. Give the chemical equation of the reaction involved.
Can we keep sodium immersed under water? Why?
Write the chemical equation of the reaction which takes place when iron reacts with dilute sulphuric acid. What happens when the gas produced is ignited with a burning matchstick?
An acidic oxide is produced by the element:
(a) Na
(b) C
(c) Ca
(d) H
You are given a solution of AgNO3. Which of the following do you think cannot displace Ag from AgNO3solution?
(a) Magnesium
(b) Zinc
(c) Gold
(d) Copper
Name a metal which does not react with cold as well as hot water but reacts with steam.
Write a chemical equation to illustrate the use of aluminium for joining cracked railway lines.
Choose the correct alternative and rewrite the following:
Which of the following is lue in colour?
Write the chemical equation for the following reaction:
Cinnabar is heated in the presence of air.
A cable manufacturing unit tested few elements on the basisof their physical properties.
| Properties | W | X | Y | Z |
| Malleable | Yes | No | No | Yes |
| Ductile | Yes | No | No | Yes |
| Electrical conductivity | Yes | Yes | Yes | No |
| Melting Point | High | Low | Low | High |
Which of the above elements were dicarded for usage by the company?
