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प्रश्न
By adding gypsum to cement
पर्याय
setting time of cement becomes less.
setting time of cement increases.
colour of cement becomes light.
shining surface is obtained.
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उत्तर
setting time of cement increases.
Explanation:
Raw materials for cement are limestone, clay and gypsum. Cement is a dirty greyish heavy powder containing calcium aluminates and silicates. Gypsum (CaSO4 – 2H2O) is added to the components to increase the setting time of cement so that it gets sufficiently hardened. Setting of cement is an exothermic process and involves hydration of calcium aluminates and silicates.
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संबंधित प्रश्न
Why are alkali metals not found in nature?
Explain why alkali and alkaline earth metals cannot be obtained by chemical reduction methods?
When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
Write a balanced equation for the reaction between KO2 and water.
Write a balanced equation for the reaction between Na2O and CO2.
Which of the alkali metal is having least melting point?
Which one of the following alkali metals gives hydrated salts?
For alkali metals, which one of the following trends is incorrect?
Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?
The solubility of metal halides depends on their nature, lattice enthalpy and hydration enthalpy of the individual ions. Amongst fluorides of alkali metals, the lowest solubility of LiF in water is due to ______.
In the synthesis of sodium carbonate, the recovery of ammonia is done by treating NH4Cl with Ca(OH)2. The by-product obtained in this process is ______.
Which of the following compounds are readily soluble in water?
(i) BeSO4
(ii) MgSO4
(iii) BaSO4
(iv) SrSO4
Choose the correct statements from the following.
(i) Beryllium is not readily attacked by acids because of the presence of an oxide film on the surface of the metal.
(ii) Beryllium sulphate is readily soluble in water as the greater hydration enthalpy of Be2+ overcomes the lattice enthalpy factor.
(iii) Beryllium exhibits coordination number more than four.
(iv) Beryllium oxide is purely acidic in nature.
The stability of peroxide and superoxide of alkali metals increase as we go down the group. Explain giving reason.
The ease of absorption of the hydrated alkali metals ions in an ion-exchange resin follows the order:
Given below are two statements, one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Lithium salts are hydrated.
Reason (R) : Lithium has higher polarising power than other alkali metal group members.
In the light of the above statements, choose the most appropriate answer from the options given below :
The correct order of conductivity of ions in water is ______.
