Advertisements
Advertisements
Question
Give reason for the following:
Though hydrogen is lighter than air it cannot be collected by downward displacement of air.
Advertisements
Solution
Since hydrogen is lighter than air. it is possible to collect the gas by downward displacement of air. But it is not safe to do so since a mixture of hydrogen and air can lead to an explosion.
RELATED QUESTIONS
Match the statements in Column A with those in Column B.
| Column A | Column B |
|
1. A metal which reacts with cold water to from hydrogen. |
1. Reduction |
| 2. A gas which is inflammable and non-supporter of combustion | 2. Hydrogenation |
|
3. A process in which vanspati ghee is prepared from vegitable oils |
3. oxidation |
|
4. The removal ofhydrogen or addition of oxygen |
4. sodium |
| 5. The addition of hydrogen or removal of oxygen | 5. Hydrogen |
For laboratory preparation of hydrogen, give the following:
method of collection
Choose the correct option:
Elements which show unique nature in the preparation of hydrogen are:
Where does hydrogen occur in a free state?
Hydrogen can be prepared with the help of cold water. Give a reaction of hydrogen with:
A monovalent metal
Hydrogen can be prepared with the help of cold water. Give a reaction of hydrogen with:
A divalent metal
Why are the following metal not used in the lab. preparation of hydrogen?
iron
Complete and balance the following reaction.
Ca + H2O →_____________ +___________
Complete and balance the following reaction.
Zn + HCl →_____________ +___________
Complete and balance the following reaction.
Al + KOH + H2O→_____________ +___________
Correct the following statement:
Hydrogen is separated from CO by passing the mixture through caustic potash solution.
‘Hydrogen is obtained by electrolysis of acidified water’.
Answer the following pertaining to the preparation of hydrogen by electrolysis,
Name the electrode –
- through which the current enters the electrolyte.
- at which hydrogen is liberated.
Give reason for the following:
In the preparation of hydrogen by electrolysis of water – the distilled water used is acidified.
On heating which of the following substances i.e. copper carbonate, zinc carbonate, washing soda, copper sulphate, zinc nitrate, copper nitrate, lead nitrate, ammonium chloride and ammonium dichromate – relate to the reaction given below.
A white substance which leaves an amphoteric oxide as a residue [whose colour varies in the heated and in the cold state] and evolves a gas which turns lime water milky.
On heating which of the following substances i.e. copper carbonate, zinc carbonate, washing soda, copper sulphate, zinc nitrate, copper nitrate, lead nitrate, ammonium chloride and ammonium dichromate – relate to the reaction given below.
An efflorescent substance which leaves a residue having the same colour as the substance and evolves a gas which changes the colour of cobalt chloride paper.
Complete and balance the equation:
[General method]
Reactions of metals - alkali [conc. soln.]
Aluminium - 2Al + 2NaOH + 2H2O → ______ + _______ [g]
2Al + 2KOH + 2H2O → _____ + _____ [g]
State the reactant added to hydrogen to obtain the respective product in following case.
Water
Give a balanced equation for the following conversion.
\[\ce{CO + H2<-H2O->CO2 + H}\]
