Answer:
83.86g/mol is the molecular weight of the acid
Explanation:
Molecular weight is the ratio of mass in grams and moles present. That means we need to determine the mass in grams (400.0mg = 0.400g) and the moles of the acid that can be detemined by using its reaction with NaOH:
<em>Moles acid:</em>
First, we need to assume the acid is a monoprotic acid (Only 1 proton is acid and reacts with a base).
when the acid, HX, reacts with NaOH there is produced:
HX + NaOH → H₂O + NaX
<em>Where 1 mole of HX reacts per mole of NaOH. That means the moles at the endpoint of NaOH = Moles of HX:</em>
<em />
Moles NaOH:
15.90mL= 0.01590L * (0.0750mol / L) = 1.193x10⁻³ moles of NaOH = Moles of HX are present.
The acidic solution was diluted to 100.0mL but only 25.00mL were taken, that is:
25.00mL / 100.00mL = 1/4 of the acid was titrated.
And moles of HX in the original solution are:
1.193x10⁻³ moles of HX * 4 = 4.77x10⁻³ moles of HX
<em>It is multiplied by 4 because the real amount of acid is 4 times the titrated amount.</em>
<em />
Thus, molecular weight is:
0.4000g / 4.77x10⁻³ moles of HX =
<h3>83.86g/mol is the molecular weight of the acid</h3>
