Advertisements
Advertisements
Questions
Compare roasting and calcination.
Distinguish between:
Roasting - Calcination
Advertisements
Solution
| Roasting | Calcination | |
| 1. | This method is generally used for sulphide ores | This method is generally used for carbonate ores. |
| 2. | In this method, ores are heated in excess of air. | In this method, ores are heated in a limited supply of air. |
| 3. | In roasting, generally sulphur dioxide gas is evolved. | In calcination, generally carbon dioxide gas is evolved. |
| 4. | In this method, sulphide ores are oxidized to form metal oxides. E.g. \[\ce{2ZnS + 3O2 -> 2ZnO + 2SO2 \uparrow}\] |
In this method, carbonate ores decompose to form metal oxide. E.g. \[\ce{ZnCO3 -> ZnO + CO2 \uparrow}\] |
APPEARS IN
RELATED QUESTIONS
What are alloys?
Give reasons:
Platinum, gold and silver are used to make jewellery.
Two methods by which rusting of iron can be prevented are ______ and ______.
Explain why rusting of iron objects is faster in coastal areas than in deserts.
Explain the term “corrosion” with an example. Write a chemical equation to show the process of corrosion of iron.
Name any three objects (or structures) which are gradually damaged by the corrosion of iron and steel.
Explain why, iron sheets are coated with zinc.
In one method of rust prevention, the iron is not coated with anything. Which is this method?
What is the corrosion of iron known as?
Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.
Name a common metal which is highly resistant to corrosion.
Brass is an alloy of ______.
Find the odd man out:
What are the adverse effects of corrosion?
Choose the correct alternative and rewrite the following:
Iron is _____________________.
Write three methods of preventing rusting of iron.
Give reason.
A wooden article should be polished.
Give reason.
Copper and brass utensils should be tinned.
Give a reason why rust turns moist red litmus blue.
State whether the statement given below is true or false. If false write the correct statement.
Graphite is a lustrous non-metal which conducts electricity.
Bronze : _______ : : Stainless steel : Fe + Cr + C
Write the name.
An alloy of copper and tin-
Write the name.
Method used to prevent corrosion of copper.
Write scientific reason.
Coins are made from metals and alloys.
Draw a neat labelled diagram.
Anodizing
What is rust?
Observe the following diagram and give answers.
- Name this method of prevention of corrosion.
- For prevention of which metal this method is used?
- What is used as anode in this method?
Observe the following diagram and write answers.
- Name the method.
- Explain the method.
- Give two examples of this method.
Give preventive methods by giving examples of corrosion?
What is rust?
Copper objects lose their shine and form green coating of ____________.
Alloys are homogeneous mixtures of a metal with a metal or non-metal. Which among the following alloys contain non-metal as one of its constituents?
Give an example of a chemical reaction for the following situation:
Sound is produced
Explain the chemical reactions in rusting of iron.
| A process of forming a thick oxide of aluminium when aluminium is exposed to air. This coat makes it resistant to corrosion. Resistance can be improved by making a layer of oxide thinker. In this technique, the aluminium article is the anode, and the electrolyte is sulphuric acid. The anode reaction results in the formation of a black-coloured film of aluminium oxide on the anode. By putting appropriate dyes in the electrolytic solution, both coloured surface with the decorative finish is achieved. Kitchen articles like anodised such as pressure cookers, pans and frames of sliding windows are applications of this technique. |
- Name the anode and electrolyte used in this technique.
- How can we make aluminium articles made resistant to corrosion?
- Name the technique used to coat the aluminium articles.
