Question:

Which of the following slows down the process of setting of the cement? 

Updated On: Aug 18, 2023
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Solution and Explanation

Gypsum plays an important role in controlling the amount of cement hardening. Because cement dries quickly, it is added to concrete and cement to slow down the drying time.
Therefore, the answer is Gypsum.
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Concepts Used:

Acids and Bases

Acid is any hydrogen-containing substance that is capable of donating a proton (hydrogen ion) to another substance. Base is an ion or molecule capable of accepting a hydrogen ion from acid. 

Physical Properties of Acids and Bases

Physical PropertiesACIDSBASES
TasteSourBitter
Colour on Litmus paper Turns blue litmus redTurns red litmus blue
Ions produced on dissociationH+OH-
pH<7 (less than 7)>7 (more than 7)
Strong acidsHCl, HNO3, H2SO4NaOH, KOH
Weak AcidsCH3COOH, H3PO4, H2CO3NH4OH

Chemical Properties of Acids and Bases

Type of ReactionAcidBases
Reaction with Metals

Acid + Metal → Salt + Hydrogen gas (H2)

E.g.,

Zn(s)+ dil. H2SO4 → ZnSO(Zinc Sulphate) + H2

Base + Metal → Salt + Hydrogen gas (H2)

E.g.,

2NaOH +Zn → Na2ZnO2 (Sodium zincate) + H2

Reaction with hydrogen carbonates (bicarbonate) and carbonates

Metal carbonate/Metal hydrogen carbonate + Acid → Salt + Carbon dioxide + Water

E.g., HCl+NaOH → NaCl+ H2O

2. Na2CO3+ 2 HCl(aq) →2NaCl(aq)+ H2O(l) + CO2(g)

3. Na2CO3+ 2H2SO4(aq) →2Na2SO4(aq)+ H2O(l) + CO2(g)

4. NaHCO3+ HCl → NaCl+ H2O+ CO2

Base+ Carbonate/ bicarbonate → No reaction
Neutralisation Reaction

Base + Acid → Salt + Water

E.g., NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Base + Acid → Salt + Water

E.g., CaO+ HCl (l) → CaCl2 (aq)+ H2O (l)

Reaction with Oxides

Metal oxide + Acid → Salt + Water

E.g., CaO+ HCl (l) → CaCl2 (aq)+ H2O (l)

Non- Metallic oxide + Base → Salt + Water

E.g., Ca(OH)2+ CO2 → CaCO3+ H2O

Dissolution in Water

Acid gives H+ ions in water.

E.g., HCl → H+ + Cl-

HCl + H2O → H3O+ + Cl–

Base gives OH- ions in water.

Read more on Acids, Bases and Salts