In beakers, obtain of the 0.1 M weak acid and of the conjugate base stock solutions. This will be your supply to make the buffer solutions.
Prepare of the assigned 1:1 buffer solution in a clean, labeled 100 mL . You will need to use of the 0.1 M weak acid and of the 0.1 M conjugate base. Measure out the stock solutions using a clean , being sure to rinse it into the waste beaker between each solution to prevent contamination.

In your pre‑lab, write out how much weak acid and conjugate base will be used to make each of the remaining buffer solutions: 1:4, 1:9, 4:1, 9:1. 250 mL 30 mL beaker

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

the answer is 0.42 is that is an option. this question provides no info