Question

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.)

Answer 1

Step-by-step 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