Question

Linolenic acid (C18H30O2) can be hydrogenated to stearic acid by reacting it with hydrogen gas according to the equation: C18H30O2 + 3H2 --->C18H36O2 What volume of hydrogen gas, measured at STP, is required to react with 10.5 g of linolenic acid in this reaction?

Answer 1

1.998 ml of hydrogen gas volume is is required to react with 10.5 g of linolenic acid in this reaction.

Explanation:

Data given:

mass of linolenic acid is given = 10.5 grams

atomic mass of linoleinic acid = 278.43 grams/mole

volume of hydrogen required at STP = ?

Balance chemical reaction:

C18H30O2 + 3H2 --->C18H36O2

moles of linoleinic acid given  = $\frac{mass}{atomic mass of 1 mole}$

putting the values in the equation:

moles of linoleinic acid = $\frac{10.5}{278.43}$

                                      = 0.037 moles

from the balanced equation:

1 mole of linoleinic acid reacts with 3 moles of hydrogen

so, 0.037 moles will react with x moles of hydrogen gas

$\frac{1}{3}$ = $\frac{0.037}{x}$

x = 0.111 moles of water

volume or mass = atomic mass x number of moles

volume of hydrogen gas= 1.998 ml