Advertisements
Advertisements
प्रश्न
Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO3, hydrogen is not liberated, why?
Advertisements
उत्तर
Concentrated nitric acid is a very strong oxidising agent. When metals are treated with concentrated nitric acid the hydrogen gas that is produced during the reaction is further oxidised to water and thus hydrogen gas is not liberated.
`"Zn"("s") + 4"HNO"_3("conc".) -> "Zn"("NO"_3)_2 + 2"NO"_2("g") + 2"H"_2"O"("l")`
APPEARS IN
संबंधित प्रश्न
Give two examples of alloys with their chemical composition.
Explain why Iron sheets are coated with zinc during galvanization.
What is anodising? Give its applications.
What type of chemical reaction is involved in the corrosion of iron?
Name any two metals which do not corrode easily.
Name two metals which resist corrosion due to the formation of a thin, hard and impervious layer of oxide on their surface.
Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
Explain how the activity series accounts for each of the following:
tendency to corrosion
What is corrosion? What are necessary conditions for corrosion?
Explain with reason:
Roasting is carried out on sulphide ores and not on carbonate ores.
Answer the following question.
a) What is meant by corrosion?
b) Write names of any two methods of prevention of corrosion.
c) In which method, metal like copper, aluminium are coated with a thin layer of their oxides by means of electrolysis.
d) Explain this method with diagram.
What is ‘rusting’?
Give reason.
An iron article should be given a coat of paint
Give reason.
Copper and brass utensils should be tinned.
Explain the term – rusting and give a word equation for the formation of rust. If polished iron nails are kept in three separate test tubes, state the contents in each test tube required, to prove the conditions for rusting.
State whether the statement given below is true or false. If false write the correct statement.
Either oxygen or moisture is essential for rusting.
Observe the following picture and answer the following questions:
- What is rust?
- Write the chemical formula of rust.
- Write the reaction of oxidation of iron at the anode.
- Write the reaction of oxidation of iron at the cathode.
- What is corrosion?
Observe the following figure and write the answer of the question.
- Which process is shown in the figure?
- Explain the chemical reaction shown in the figure.
- Write the reactions on anode and cathode.
Amalgam is an alloy of ____________.
Describe two changes that are harmful. Explain why you consider them harmful. How can you prevent them?
