7) A Mohr titration is a precipitation titration used to analyze the amount of $\mathrm{Cl}^{-}$or $\mathrm{Br}^{-}$ions in a sample. The titrant is silver nitrate $\left(\mathrm{AgNO}_{3}\right)$ and reacts with the chloride ions to form a white silver chloride $(\mathrm{AgCl})$ precipitate according to the following reaction: \[ \mathrm{Ag}_{(\mathrm{aq})}+\mathrm{Cl}_{(\mathrm{aq})} \rightarrow \mathrm{AgCl}_{(\mathrm{s})} \] If potassium chromate $\left(\mathrm{K}_{2} \mathrm{CrO}_{4}(\mathrm{aq})\right)$ is added as an indicator, after all of the $\mathrm{AgCl}$ has formed, an orange/red precipitate (silver chromate, $\mathrm{Ag}_{2} \mathrm{CrO}_{4}$ ) will appear at the end point according to this reaction: \[ 2 \mathrm{Ag}_{(\mathrm{aq})}+\mathrm{CrO}_{4(\mathrm{aq})} \rightarrow \mathrm{Ag}_{2} \mathrm{CrO}_{4(\mathrm{~s})} \] A student placed $50.00 \mathrm{~mL}$ of a water sample into an Erlenmeyer flask. Three drops of $\mathrm{K}_{2} \mathrm{CrO}_{4}$ (aq) were then added to the flask. The buret contained $0.080 \mathrm{M}$ $\mathrm{AgNO}_{3}(\mathrm{aq})$ as the titrant. If $15.70 \mathrm{~mL}$ of titrant was used to reach the end point, calculate the amount of chloride ions in Analyte containing $\mathrm{K}_{2} \mathrm{CrO}_{4}$ indicator White $\mathrm{AgCl}$ precipitate Orange/red $\mathrm{Ag}_{2} \mathrm{CrO}_{4}$ precipitate $\mathrm{mg} / \mathrm{L}$ found in the sample.

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