Problem 62
What volume of \(0.25 \mathrm{M} \mathrm{NaOH}\) contains \(0.050 \mathrm{~mol}\) \(\mathrm{NaOH}\) ?
Problem 63
A solution contains \(20.5 \mathrm{~g}\) of sodium chloride dissolved in sufficient water to give a total mass of \(166.2 \mathrm{~g}\). What is the molality of this solution?
Problem 64
How many moles of sucrose, \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\), are contained in \(50.0 \mathrm{~g}\) of a \(0.85 \mathrm{~m}\) sucrose solution?
Problem 65
What is the molar concentration of ions in a \(1.5 M \mathrm{KNO}_{3}\) solution? What is the molal concentration of ions in a \(1.5 \mathrm{~m} \mathrm{KNO}_{3}\) solution?
Problem 66
What is the molar concentration of ions in a \(2.5 \mathrm{M} \mathrm{MgCl}_{2}\) solution? What is the molal concentration of ions in a \(2.5 \mathrm{~m} \mathrm{MgCl}_{2}\) solution?
Problem 67
A \(250.0-\mathrm{g}\) sample of pond water contains \(2.4 \mathrm{mg}\) arsenic. What is the mass percent of arsenic in the pond? How many parts per million of arsenic are in the pond? How many parts per billion?
Problem 68
A \(375.0\)-g sample of river water taken near an industrial plant contains \(37 \mathrm{mg}\) of chromium. What is the mass percent of chromium in the river? How many parts per million of chromium are in the river? How many parts per billion?
Problem 69
Drinking water may contain a low concentration of lead ion, \(\mathrm{Pb}^{2+}\), due to corrosion of old lead pipes. The EPA has determined that the maximum safe level of lead ion in water is \(15 \mathrm{ppb}\). Suppose a sample of tap water was determined to have a lead ion concentration of \(0.0090 \mathrm{ppm}\). Assume the density of the solution is \(1.00 \mathrm{~g} / \mathrm{mL}\). (a) What is the concentration of lead ion in the tap water in units of \(\mathrm{ppb}\) ? Is it safe to drink? (b) What is the concentration of lead ion in units of \(\mathrm{mg} / \mathrm{mL}\) ? (c) What mass of lead ion is in \(100.0 \mathrm{~mL}\) of this drinking water? (d) How many moles of lead ion are in \(100.0 \mathrm{~mL}\) of the water?
Problem 70
Excessive levels of nitrates found in drinking water can cause serious illness. When nitrates are converted to nitrites in the body, the nitrites can interfere with the oxygen-carrying capacity of the blood, causing blueness of the skin. The EPA has determined that the maximum safe level of nitrate ion in water is \(10 \mathrm{ppm}\). Suppose a sample of tap water was determined to have a nitrate ion concentration of \(95 \mathrm{ppb}\). Assume the density of the solution is \(1.00 \mathrm{~g} / \mathrm{mL}\). (a) What is the concentration of nitrate ion in units of ppm? Is it safe to drink? (b) What is the concentration of nitrate ion in units of \(\mathrm{mg} / \mathrm{mL}\) ? (c) What mass of nitrate ion is in \(100.0 \mathrm{~mL}\) of this drinking water? (d) How many moles of nitrate ion are in \(100.0 \mathrm{~mL}\) of the water?
Problem 71
One way to remove lead ion from water is to add a source of iodide ion so that lead iodide will precipitate out of solution: $$ \mathrm{Pb}^{2+}(a q)+2 \mathrm{I}^{-}(a q) \longrightarrow \mathrm{PbI}_{2}(s) $$ (a) What volume of a \(1.0 \mathrm{M} \mathrm{KI}\) solution must be added to \(100.0 \mathrm{~mL}\) of a solution that is \(0.15 \mathrm{M}\) in \(\mathrm{Pb}^{2+}\) ion to precipitate all the lead ion? (b) What mass of \(\mathrm{PbI}_{2}\) should precipitate?
