Un insecticide à base de DDT (dont la formule brute est C14 H9 Cl5 ) est annoncé en contenir 1 %

step 1 To calculate the mass percent to 4D, the first thing we'll do is we'll take the mass of the fina

Un insecticide à base de DDT (dont la formule brute est C14...

Un insecticide à base de DDT (dont la formule brute est $\mathrm{C}_{14} \mathrm{H}_9 \mathrm{Cl}_5$ ) est annoncé en contenir $1 \%$. Afin de vérifier s'il contient la quantité prévue de produit actif, il est soumis à une expertise pour laquelle on procède ainsi : un échantillon d'insecticide de $0,73 \mathrm{~g}$ est traité de façon à minéraliser le chlore du DDT, c'est-à-dire à le transformer entièrement en ions $\mathrm{Cl}^{-}$. En présence de nitrate d'argent $\mathrm{AgNO}_3$ en excès, ces ions sont intégralement inclus dans un précipité de chlorure d'argent $\mathrm{AgCl}$, qu'on filtre, sèche et pèse. La masse de $\mathrm{AgCl}$ ainsi obtenue est $14 \mathrm{mg}$, cet insecticide est-il conforme à la composition annoncée?

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Key Concepts

Precipitation Reaction

A precipitation reaction is a chemical process where soluble ions in solution react to form an insoluble solid, known as a precipitate. This reaction is typically used in qualitative and quantitative analysis to separate or identify ions by forming a compound that can be isolated from the reaction mixture.

Percent Composition

Percent composition refers to the mass percentage of a particular component relative to the total mass of a sample or compound. It is a critical concept in analytical chemistry for assessing the purity and compliance of substances with their advertised concentrations.

Stoichiometry

Stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. By using balanced chemical equations, stoichiometry enables the calculation of how much product can be formed from a given amount of reactant, and it is essential for converting between masses, moles, and numbers of particles.

Gravimetric Analysis

Gravimetric analysis is an analytical method that involves converting an analyte into a compound of known composition that can be isolated and weighed. This technique is used to determine the amount of a specific component in a sample by precipitating it as an insoluble product, filtering, drying, and then accurately weighing the precipitate.

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