Why is a chemical indicator added to the flask in which a titration will occur? a to show when enough base has been added b to determine the starting ph of the solution c to neutralize the acid before adding the base d to identify the starting volume of acid

Option (a) is the correct answer.

Explanation:

An indicator is a substance whose color changes in certain situations. An indicator, when added to the unknown concentration of an acid changes its color on addition of enough standard solution of a base.

For example, when an indicator is added into an acidic solution and titrated with a base then, the color of acidic solution will change at a certain point. Hence, the change in color  indicates that enough base has been added to the acidic solution.

Different indicators show different color in acidic or basic medium

Thus, to show when enough base has been added a chemical indicator will be added to the flask in which titration will occur.

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g