Answer:
A mixture of 100. mL of 0.1 M HC3H5O3 and 50. mL of NaOH
Explanation:
The pH of a buffer solution is calculated using following relation

Thus the pH of buffer solution will be near to the pKa of the acid used in making the buffer solution.
The pKa value of HC₃H₅O₃ acid is more closer to required pH = 4 than CH₃NH₃⁺ acid.
pKa = -log [Ka]
For HC₃H₅O₃
pKa = 3.1
For CH₃NH₃⁺
pKa = 10.64
pKb = 14-10.64 = 3.36 [Thus the pKb of this acid is also near to required pH value)
A mixture of 100. mL of 0.1 M HC3H5O3 and 50. mL of NaOH
Half of the acid will get neutralized by the given base and thus will result in equal concentration of both the weak acid and the salt making the pH just equal to the pKa value.
Answer:
The molecular formula of an ascenapthalene is 
Explanation:


where,
=Elevation in boiling point = 
Mass of acenapthalene = 0.515 g
Mass of
= 15.0 g = 0.015 kg (1 kg = 1000 g)
= boiling point constant = 3.63 °C/m
m = molality
Now put all the given values in this formula, we get


Let the molecule formula of the Acenapthalene be ![C_{6n]H_{5n}](https://tex.z-dn.net/?f=C_%7B6n%5DH_%7B5n%7D)

n = 2.0
The molecular formula of an ascenapthalene is 
Answer: 78.919 amu
Explanation:
If the natural abundance of Br-81 is 49.310%, then the natural abundance of Br-79 must be 100%-49.310%=50.690%
Substituting into the atomic mass formula,
