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Chapter 11: Problem 1

Practise calculations involving molar concentrations (see also study exercises \(9.1\) and 9.2). What mass of substance would be required to prepare each of the following aqueous solutions (answer in grams, to four decimal places in each case): (a) \(1000.00 \mathrm{~mL}\) of \(1.0 \mathrm{M}\) sodium chloride solution? (b) \(250.00 \mathrm{~mL}\) of \(0.2004 \mathrm{M} \mathrm{KMnO}_{4}\) solution? (c) \(400 \mathrm{~mL}\) of sodium hydroxide at \(5 \% \mathrm{w} / \mathrm{v} ?\) (d) \(300 \mathrm{~mL}\) of potassium nitrate at \(10 \% \mathrm{w} / \mathrm{w} ?\)

Short Answer

Expert verified
a) 58.4400 g, b) 7.9206 g, c) 20.0000 g, d) 30.0000 g

Step by step solution

01

Calculate the mass of sodium chloride

Molarity (M) is defined as the number of moles of solute per litre of solution. Therefore, to find the mass of sodium chloride required for a 1.0 M solution in 1000.00 mL, first convert mL to L then multiply the molarity by the volume in litres and the molar mass of sodium chloride (58.44 g/mol), \( mass = Molarity \times Volume \times Molar~mass =1.0 \times 1.0 \times 58.44 = 58.44 g\).
02

Calculate the mass of KMnO4

For 0.0004 M KMnO4 solution in 250 mL, convert mL to L, then multiply the molarity by the volume in litres and the molar mass of KMnO4 (158.03 g/mol), \( mass = Molarity \times Volume \times Molar~mass = 0.2004 \times 0.25 \times 158.033 = 7.9206 g \).
03

Calculate the mass of sodium hydroxide

For a 5% w/v solution of sodium hydroxide in 400 mL, the mass (in grams) of sodium hydroxide is 5% of the volume (in mL), \( mass = \frac{5}{100} \times 400 = 20 g \).
04

Calculate the mass of potassium nitrate

For a 10% w/w solution of potassium nitrate in 300 mL, first you convert mL to g (assuming the density of water is about 1 g/mL), then calculate the mass (in grams) of potassium nitrate which is 10% of the converted mass, \( mass = \frac{10}{100} \times 300 = 30 g \).

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Most popular questions from this chapter

Using the concepts of 'oxidation numbers' and 'partial ionic equations', balance the following redox reactions which all take place in acid solution. (a) \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+\mathrm{FeSO}_{4}+\mathrm{H}_{2} \mathrm{SO}_{4}\) $$ \rightarrow \mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}+\mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}+\mathrm{K}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O} $$ (b) \(\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}+\mathrm{I}_{2} \rightarrow \mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}+\mathrm{Nal}\) (c) \(\mathrm{KIO}_{3}+\mathrm{KI}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{K}_{2} \mathrm{SO}_{4}+\mathrm{I}_{2}+\mathrm{H}_{2} \mathrm{O}\) (d) \((\mathrm{COOH})_{2}+\mathrm{KMnO}_{4}+\mathrm{H}_{2} \mathrm{SO}_{4}\) $$ \rightarrow \mathrm{K}_{2} \mathrm{SO}_{4}+\mathrm{MnSO}_{4}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} $$

Practise expressing concentrations in different ways. Express all answers to four decimal places. (a) What is \(4.000 \mathrm{~g} \mathrm{~L}^{-1}\) sodium hydroxide expressed in terms of molarity? (b) What is \(0.1\) mol \(\mathrm{L}^{-1} \mathrm{~K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) expressed in \(g L^{-1} ?\) (c) What is \(5 \% \mathrm{v} / \mathrm{v}\) ethanol, expressed in terms of molarity? (Density of ethanol at \(\left.25^{\circ} \mathrm{C}=0.7892 \mathrm{~g} \mathrm{~mL}^{-1}\right)\) (d) What is \(150 \mathrm{mmol} \mathrm{L}^{-1}\) glucose expressed in terms of per cent concentration \((\% \mathrm{w} / \mathrm{v}) ?\)
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