Advertisements
Advertisements
प्रश्न
By adding gypsum to cement
विकल्प
setting time of cement becomes less.
setting time of cement increases.
colour of cement becomes light.
shining surface is obtained.
Advertisements
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.
APPEARS IN
संबंधित प्रश्न
Why are alkali metals not found in nature?
Explain why alkali and alkaline earth metals cannot be obtained by chemical reduction methods?
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
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?
What are the common physical features of alkali metals?
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
When heated in air, the alkali metals form various oxides. Mention the oxides formed by Li, Na and K.
Write Lewis strucure of \[\ce{O^{-}2}\] ion and find out oxidation state of each oxygen atom? What is the average oxidation state of oxygen in this ion?
When a metal of group 1 was dissolved in liquid ammonia, the following observations were obtained:
(i) Blue solution was obtained initially.
(ii) On concentrating the solution, blue colour changed to bronze colour.
How do you account for the blue colour of the solution? Give the name of the product formed on keeping the solution for some time.
The valence shell electronic configuration of alkali metals is ______.
A white precipitate was formed when BaCl2 was added to extract of an inorganic salt. Farther, a gas 'X' with characteristic odour was released when the formed white precipitate was dissolved in dilute HCl. The anion present in the inorganic salt is ______.
The metal mainly used in devising photoelectric cells is ______.
The correct order of conductivity of ions in water is ______.
KO2 (potassium super oxide) is used in oxygen cylinders in space and submarines because it ______.
