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Chapter 5: Problem 15

How many milligrams of \(\mathrm{MgI}_{2}\) must be added to \(250.0 \mathrm{mL}\) of \(0.0876 \mathrm{M} \mathrm{KI}\) to produce a solution with \(\left[\mathrm{I}^{-}\right]=0.1000 \mathrm{M} ?\)

Short Answer

Expert verified
To achieve the solution with a desired I- concentration of 0.1 M, approximately 1.74 g or 1740 mg of MgI2 must be added to the 250 mL of 0.0876 M KI solution.

Step by step solution

01

Calculate initial moles of I- ions in KI

We can calculate the initial amount of I- ions in KI by using the formula for molarity and the volume. The formula for molarity is \[Molarity = \frac{Moles}{Volume}\]. Hence, moles are calculated by multiplying molarity (0.0876 M) with volume (0.250 L, converted from ml).
02

Calculate final moles of I- ions required

To find the number of I- ions required in the final solution, multiply the final volume (0.250 L) with the desired molarity (0.1000 M). The difference between the final and initial moles will provide the moles of I- ions that should come from MgI2. Here, each MgI2 molecule dissociates to give 2 I- ions.
03

Calculate the mass of MgI2 to be added

Once the moles of I- ions from MgI2 are known, these can be converted into mass by using the molar mass of MgI2 (278.11 g/mol). The mole-to-mass conversion is done by multiplying the moles with the molar mass. Convert this mass from grams to milligrams by multiplying by 1000.

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Most popular questions from this chapter

Which aqueous solution has the greatest \(\left[\mathrm{H}^{+}\right]:\) (a) \(0.011 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH} ;\) (b) \(0.010 \mathrm{M} \mathrm{HCl} ;\) (c) \(0.010 \mathrm{M}\) \(\mathrm{H}_{2} \mathrm{SO}_{4} ;\) (d) \(1.00 \mathrm{M} \mathrm{NH}_{3} ?\) Explain your choice.

Balance these equations for redox reactions occurring in acidic solution. (a) $\mathrm{P}_{4}(\mathrm{s})+\mathrm{NO}_{3}^{-} \longrightarrow \mathrm{H}_{2} \mathrm{PO}_{4}^{-}+\mathrm{NO}(\mathrm{g})$ (b) $\mathrm{S}_{2} \mathrm{O}_{3}^{2-}+\mathrm{MnO}_{4}^{-} \longrightarrow \mathrm{SO}_{4}^{2-}+\mathrm{Mn}^{2+}$ (c) $\mathrm{HS}^{-}+\mathrm{HSO}_{3}^{-} \longrightarrow \mathrm{S}_{2} \mathrm{O}_{3}^{2-}$ (d) $\mathrm{Fe}^{3+}+\mathrm{NH}_{3} \mathrm{OH}^{+} \longrightarrow \mathrm{Fe}^{2+}+\mathrm{N}_{2} \mathrm{O}(\mathrm{g})$

Assuming the volumes are additive, what is the \(\left[\mathrm{NO}_{3}^{-}\right]\) in a solution obtained by mixing \(275 \mathrm{mL}\) of \(0.283 \mathrm{M} \mathrm{KNO}_{3}, 328 \mathrm{mL}\) of \(0.421 \mathrm{M} \mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2},\) and \(784 \mathrm{mL}\) of \(\mathrm{H}_{2} \mathrm{O} ?\)

What volume of \(0.0962 \mathrm{M} \mathrm{NaOH}\) is required to exactly neutralize \(10.00 \mathrm{mL}\) of \(0.128 \mathrm{M} \mathrm{HCl} ?\)

Sodium hydroxide used to make standard \(\mathrm{NaOH}(\mathrm{aq})\) solutions for acid-base titrations is invariably contaminated with some sodium carbonate. (a) Explain why, except in the most precise work, the presence of this sodium carbonate generally does not seriously affect the results obtained, for example, when \(\mathrm{NaOH}(\mathrm{aq})\) is used to titrate HCl(aq). (b) Conversely, show that if \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) comprises more than \(1 \%\) to \(2 \%\) of the solute in NaOH(aq), the titration results are affected.
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