some chem questions!!!!!!!!!!!!!!

1.
Sodium carbonate is an alkali because carbonate ion can hydrolyzed in water to give OH-(aq) ion.
CO32-(aq) + H2O(l) = HCO3-(aq) + OH-(aq)
An alkali is a substance which can be dissociated in water to give OH-(aq) ion. Therefore, sodium carbonate is an alkali, and its solution is alkaline.

2.
Effervescence means the phenomenon that gas bubbles are formed. The bubbles can be hydrogen, carbon dioxide, or any gas else.

3.
Calcium hydroxide dissociates in water to give calcium ion and hydroxide ion.
Ca(OH)2(s) + aq → Ca2+(aq) + 2OH-(aq)
An alkali is a substance which can be dissociated in water to give OH-(aq) ion. Therefore, calcium hydroxide is an alkali, no matter whether how low the solubility is.

4.
Pipettes have different capacities. The commonest capacity is 25 cm3.

5.
In dilute acid, the acid is the solute, and water is the solvent.
When water is added to the dilute acid, the amount of the solvent (water) is increased, but the amount of the solute (acid) is unchanged.