Some Basic Conc...

$$2K(s)+2{H}_{2}O(l)\rightarrow 2KOH(aq)+{H}_{2}(g)$$
If $$3.0$$ moles of potassium react with excess water, what volume of hydrogen gas will be produced?

Use the figure below to answer the question that follows.
Which of the four molecules has the highest percentage of nitrogen, by mass?

A $$5.0g$$ sample of copper(II) oxide containing an inert contaminant is analyzed and found to contain $$3.0g\ Cu$$. Using molar masses of $$64g/mol$$ for copper, and $$16g/mol$$ for oxygen, determine the percent purity of the copper(II) oxide sample.

A student would like to use gravimetric analysis to determine the percent by mass of magnesium chloride in a contaminated mixture containing magnesium chloride.
Which of the following compounds would be the BEST substance to react the contaminated mixture with to determine the mass percent?

A hydrate sample of magnesium chloride is analyzed and found to contain $$53.18$$% water.
How many water molecules are found in the formula for this hydrate?

What is the correct unit for the following solution?

What would be the approximate weight of $$1.204\times 10^{24}$$ bromine atoms?

If a copper-containing compound contains $$4.999$$% $$Cu$$ by mass and there are $$2$$ copper atoms per formula unit, what is the molar mass of the compound?

Which pair of substances share the same mass percent of each element?

How many atoms of hydrogen are present in $$7.8\ g$$ of $$Al{(OH)}_{3}$$?