Barium sulfate contains barium ions, Ba$^{2+}$ sulfate ions, SO$_4^{2-}$ - Edexcel - GCSE Chemistry - Question 5 - 2013 - Paper 1

An ion is defined as a charged particle, which can be either an atom or a molecule that has gained or lost one or more electrons, resulting in a net electrical charge.

Barium sulfate is insoluble in water, which means it does not dissolve into the bloodstream. This property allows it to pass through the body unchanged without being absorbed or causing toxicity. Therefore, it remains in the gastrointestinal tract where it can effectively outline areas for X-ray imaging.

To prepare a pure, dry sample of barium sulfate, follow these steps:

1. Reactants Preparation: Measure equal amounts of barium chloride (BaCl$_2$) crystals and sodium sulfate (Na$_2$SO$_4$) crystals.
2. Mixing Reactants: Dissolve each reactant in a separate beaker of distilled water to create two solutions.
3. Mix Solutions: Pour the barium chloride solution into the sodium sulfate solution while stirring to ensure thorough mixing. This will cause barium sulfate to precipitate out.
4. Filtering the Precipitate: Set up a filter funnel with filter paper. Pour the mixture through the filter to collect the solid barium sulfate on the filter paper.
5. Washing the Precipitate: Rinse the barium sulfate on the filter paper with distilled water to remove any impurities.
6. Drying the Sample: Allow the barium sulfate to dry by leaving it in a warm place or placing it in an oven at a low temperature until completely dry.

The balanced chemical equation for the reaction between barium and chlorine is: [ \text{Ba} + \text{Cl}_2 \rightarrow \text{BaCl}_2 ]