The answer is each indicator has a narrow range. We need many different indicators to span the entire ph spectrum because each indicator has a narrow range.
Answer:

Explanation:
Bases are the species which furnish hydroxide ions in the solution or is capable of forming bonds with electron deficient species as they are electron rich species. When a base accepts a proton, it changes into a acid which is known as its conjugate acid.
Net ionic equation : In the net ionic equations, we are not include the spectator ions in the equations. Only the species which are present in aqueous state dissociate. So, the net ionic equation of aqueous solution of ammonia is shown below as:-

It is not important to accurately measure the amount of HCl placed in the eudiometer tube since HCl will be added in excess to react with all the moles of Mg.
In gas stoichiometry, through the method of displacement of a liquid (generally water), the gaseous byproduct is collected inside a long, thin graded glass tube called a eudiometer.
If we consider a reaction between Magnesium and Hydrochloric acid to give a product known as magnesium chloride and hydrogen gas, we can have the chemical equation represented as:

From the above reaction, for each mole of Magnesium taking place in the reaction, 1 mole of hydrogen gas is also produced.
Thus, we can have a prediction that HCl can always be added in excess in order for us to react to all the moles of solid magnesium, hence, it is not important to measure the moles of HCl since it will be added in excess.
Learn more about gas stoichiometry here:
brainly.com/question/32160?referrer=searchResults
You should of might do this first take a picture of the problem to make it easy for us to understand just saying for the furture