<u>Answer:</u> The volume of acid should be less than 100 mL for a solution to have acidic pH
<u>Explanation:</u>
To calculate the volume of acid needed to neutralize, we use the equation given by neutralization reaction:

where,
are the n-factor, molarity and volume of acid which is HCl
are the n-factor, molarity and volume of base which is NaOH
We are given:

Putting values in above equation, we get:

For a solution to be acidic in nature, the pH should be less than the volume of acid needed to neutralize.
Hence, the volume of acid should be less than 100 mL for a solution to have acidic pH
Answer:
he average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance
The compound formed by chlorine and barium is
as the number of valence electrons in barium is 2 and in chlorine is 1. In this compound, barium acts as a cation and chlorine acts as an anion. The formation of the compound is as shown in the image.
Since, barium is an element of Group-2 (alkaline earth metal) so the other element that has a chemical formula most and least similar to the chemical formula of the compound formed by chlorine and barium should be from Group-2 (alkaline earth metal) only which has properties somewhat like barium. So, the element is strontium.
Strontium forms a compound with formula
in which strontium acts as a cation and chlorine acts as an anion. The formation of the compound is as shown in the image.