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What is the difference between the empirical and molecular formulas of a compound? Can they ever be the same? Explain.

A substance \(\mathrm{A}_{2} \mathrm{B}\) is \(60 \%\) A by mass. Calculate the percent B (by mass) for \(\mathrm{AB}_{2}\).

Give the formula for calcium phosphate and then answer the following questions: a. Calculate the percent composition of each of the elements in this compound. b. If you knew that there was \(50.0 \mathrm{g}\) of phosphorus in your sample, how many grams of calcium phosphate would you have? How many moles of calcium phosphate would this be? How many formula units of calcium phosphate?

How many molecules of water are there in a \(10.0-\mathrm{g}\) sample of water? How many hydrogen atoms are there in this sample?

Why do we need to count atoms by weighing them?

Suppose Avogadro's number was 1000 instead of \(6.022 \times 10^{23} .\) How, if at all, would this affect the relative masses on the periodic table? How, if at all, would this affect the absolute masses of the elements?

Consider separate equal mass samples of magnesium, zinc, and silver. Rank them from greatest to least number of atoms and support your answer.