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प्रश्न
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be:
पर्याय
calcium
carbon
silicon
iron
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उत्तर
calcium
Explanation:
Calcium (Ca) combines with oxygen to form Calcium oxide (CaO) with a very high melting point. It dissolves in water to form Calcium hydroxide.
\[\ce{2Ca + O2 -> 2CaO}\]
\[\ce{CaO + H2O -> \underset{(soluble)}{\underset{Calcium hydroxide}{Ca(OH)2}}}\]
संबंधित प्रश्न
Iron is
(a) More reactive than zinc
(b) More reactive than aluminium
(c) Less reactive than copper
(d) Less reactive than aluminium
Why is sodium kept immersed in kerosene oil?
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
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.
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?
Name the metal which has been placed at the top of the reactivity series.
What type of oxides are formed when metals combine with oxygen? Explain with the help of an example.
Can we keep sodium immersed under water? Why?
Which gas is produced when dilute hydrochloric acid is added to a reactive metal?
Name two metals (other than zinc and iron) which can displace hydrogen from dilute hydrochloric acid?
What is the action of water on aluminium ? Write equation of the chemical reaction involved.
Write one reaction in which aluminium oxide behaves as a basic oxide and another in which it behaves as an acidic oxide.
What is meant by the reactivity series of metals? Arrange the following metals in an increasing order of their reactivities towards water:
Zinc, Iron, Magnesium, Sodium
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
The least reactive metal among the following is:
(a) sodium
(b) silver
(c) copper
(d) lead
The elements whose oxides can turn litmus solution blue are:
(a) carbon and sulphur
(b) sodium and carbon
(c) potassium and magnesium
(d) magnesium and sulphur
Which of the following reactions will not occur? Why not?
(a) MgSO4 (aq) + Cu (s) → CuSO4 (aq) + Mg (s)
(b) CuSO4 (aq) + Fe (s) → FeSO4 (aq) + Cu (s)
(c) MgSO4 (aq) + Fe (s) → FeSO4 (aq) + Mg (s)
Choose the correct alternative and rewrite the following:
Which of the following is lue in colour?
Write the chemical equation for the following reaction:
Manganese dioxide is heated with aluminum powder.
