You are asked to identify compound x, which was extracted from a plant seized by customs inspectors. you run a number of tests and collect the following data. compound x is a white, crystalline solid. an aqueous solution of x turns litmus red and conducts electricity poorly, even when x is present at appreciable concentrations. when you add sodium hydroxide to the solution a reaction takes place. a solution of the products of the reaction conducts electricity well. an elemental analysis of x shows that the mass percentage composition of the compound is 26.68% c and 2.239% h, with the remainder being oxygen. a mass spectrum of x yields a molar mass of 90.0 g mol"1. (a) write the empirical formula of x. (b) write the molecular formula of x (c) write the balanced chemical equation and the net ionic equation for the reaction of x with sodium hydroxide. (assume that x has two acidic hydrogen atoms.)

Explanation:

Compound X must be acidic  since it turns litmus red.

It must be covalent because it conducts electricity poorly even at high concentrations.

The observation that X reacts with NaOH confirms is an acid, and the products of this reactions must conduct electricity since we know the reaction of an acid with a base produces salt (the ions of the salt are in solution) and water:

HX + NaOH ⇒Na⁺ + X⁻ + H₂O

a)Empirical Formula:

Calculate the proportion of atoms given the composition and express it in integers.

Atomic Weights (g/mol) : C=12, H=1, O=16

In 100 g X :

26.68 g C / 12 g/mol = 2.22   ⇒   C:   2.22/2.22 = 1

2.239 g H / 1 g/mol =   2.24          H:  2.24/2.22 ≅ 1

71.08 g O / 16g/mol =  4.44           O:  4.44/2.22 = 2

Empirical Formula : CHO₂

b) Molar mass empirical formula = 45 g/mol ; molar mass = 90.0 g/mol ∴ Molecular formula X =  C₂H₂O₄

c) H₂C₂O₄ + NaOH ⇒ C₂O₄²⁻ + 2Na⁺ + H₂O

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.