Answer:
Mass of the unknown acid is 4.0g
Explanation:
The determine the molar mass of the unknown acid, the steps below can be followed
Firstly, determine the concentration of the acid, the formula below can be used;
ConcA × Va/ConcB × Vb = Na/Nb
Where ConcA is the concentration of the unknown acid
ConcB is the concentration of the NaOH base
Va is the volume of acid and Vb is the volume of base
Since, the titration was said to have reached an equivalent point, it means the number of moles of the acid (Na) was equal to the number of moles of the base (Nb) and thus both will be assumed to be 1
Thus
ConcA × 250/0.13 × 6.6 = 1/1
ConcA = 0.13 × 6.6/250
ConcA = 0.003432M
Then, determine the actual number of moles (n) of the unknown acid used,
ConcA = no of moles of acid/volume of acid (in dm³ or L)
To convert mL to L, we divide by 1000
Hence, 250ml = 0.25L
0.003432 = n/0.25
n = 0.003432 × 0.25
n = 0.01373 moles
To determine the molar mass;
n = mass/molar mass
The mass was given in the question to be 0.055g
Thus
0.01373 = 0.055/molar mass
molar mass = 0.055/0.01373
molar mass = 4.0g
