91Ó°ÊÓ

A sample of stainless steel, which is an alloy of iron, chromium, and minor amounts of other components, is \(11.5 \%\) by mass chromium. How many grams of chromium are there in \(250.0 \mathrm{lb}\) of stainless steel?

Suppose \(20.0 \mathrm{~g}\) of \(\mathrm{NaBr}(\mathrm{s})\) is added to \(50.0 \mathrm{~mL}\) of a \(2.00 \mathrm{M}\) silver nitrate solution. (a) Write a net ionic equation for the formation of the expected precipitate. (b) What is the theoretical yield of precipitate in grams? (c) Suppose only \(15.0 \mathrm{~g}\) of precipitate is isolated. What is the percent yield for the reaction? (d) What is the molar concentration of the excess reactant in the combined solution?

In a titration of \(\mathrm{HCl}\) with \(\mathrm{NaOH}\), you read the buret to see how much base it took to neutralize the acid (turn the indicator pink). You do this titration to determine the molar concentration of the acid. Why is it important to accurately know the amount (volume) of acid that you originally put into the flask?

When methanol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right)\) dissolves in water, both initially at \(22{ }^{\circ} \mathrm{C}\), heat is released and the resulting solution is warmer than \(22{ }^{\circ} \mathrm{C}\). Explain why this is so. (What must be true?)

At \(0.00{ }^{\circ} \mathrm{C}\) and sea level, dry air can be assumed to have a molar volume of \(22.414 \mathrm{~L}\). Given that air is \(21.0 \%\) by volume oxygen, what is the molar concentration of oxygen in the atmosphere at sea level at \(0.00^{\circ} \mathrm{C}\) ?

The amount to which a solvent's boiling point is elevated and vapor pressure is lowered depends on the number per volume (concentration) and not the chemical identity of solute particles dissolved in it. Explain why this is so in terms of entropy.

The dissolving of a solute (like \(\mathrm{NaCl}\) ) into a solvent (like water) can be thought of as a threestep process. (a) Briefly name or describe these three steps. (b) What are the energy implications of each step? (exothermic, endothermic, depends on the particular solvent/solute) (c) Which of the three steps is primarily responsible for the "like dissolves like" rule for solubility?