Help with ap chemistry?

Question

By titration, 15.0 mL of 0.1008 M sodium hydroxide is needed to neutralize a 0.2053 gram sample of an organic acid. The acid is monoprotic.

a. Write down the net ionic equation of sodium hydroxide dissociating in water

b. What is the total number of moles of ions in the sodium hydroxide solution?

c. What is the molar mass of the organic acid?

d. The acid can be combusted. The products of combustion show that it is 5.89% H, 70.6% C and 23.5% O by mass.

i. What is the empirical formula of the compound?

ii. What is the molecular formula of the compound?

iii. Write the balanced molecular formula of the combustion of the compound

Answer 1

NaOH >> Na+ + OH-

moles OH- = 0.0150 L x 0.1008 M =0.001512

= moles organic acid

molar mass = 0.2053 g/ 0.001512 =135.8

g/mol

Moles H = 5.89 / 1.008 =5.84

Moles C = 70.6 / 12.011 =5.88

Moles O = 23.5 / 15.9994 =1.47

5.84 / 1.47 = 4 => H

5.88/ 1.47 = 4 => C

1.47 / 1.47 = 1 => O

C4H4O is the empirical formula ( MM = 68.07 g/mol)

135.8 / 68.07 = 2

we multiply by 2 the empirical formula

C8H8O2 is the molecular formula

C8H8O2 +9 O2 >> 8 CO2 + 4H2O