I. Good things to know
• stoichiometry, chemical formula
• ionic compound formula unit
• hydrate, anhydrous
• molecular compound molecule
• mole, Avagadro’s Number
• formula mass, molar mass, molecular mass
• Standard Temperature and Pressure (STP)
• percent yield
• limiting reactant, excess reactant
• Law of Definite Proportions, Law of Multiple Proportions
• empirical formula, molecular formula
• mass spectrometer
• titration, standard solution, unknown solution
II. Problems
1) Calculate the formula mass for:
a) HF b) SiO2 c) SiF4
1 + 19 = 20.0 28.1 + 32 = 60.1 28.1 + 4(19) = 104
2) Calculate the number of moles of HF molecules in:
a) 0.385 g HF b) 3.02 x 1024 molecules of HF
c) 50.0 mL of a 0.600M HF solution d) 1.50L of HF at 0.989 atm of pressure
and 23.1oC
3) Answer the following questions using the following equation:
4 HF(g) + 1 SiO2(s) 1 SiF4(s) + 2 H2O(l)
a) balance the equation
b) How many grams of silicon tetrafluoride will you get if you react 5.00g of silicon dioxide with
excess HF?
c) How many grams of silicon tetrafluoride will you get if you react 5.00g of silicon dioxide with
5.00g of HF? How many grams of the excess reactant will be left over?
d) If you actually produce 5.92g of silicon tetrafluoride in problem (c), what is the percent yield?
4) Find the percent composition of:
a) SiO2 28.1 + 2(16) = 60.1 b) Ba(NO3)2 137 + 2(14) + 6(16) = 261
5) How would you prepare 1.00 L of a 4.00 M H2SO4 solution from concentrated H2SO4 (18 M)?
6) A sample of 0.6760g of an unknown compound containing barium ions (Ba+2) is dissolved in water
and treated with an excess of Na2SO4. If the mass of the barium sulfate precipitate formed is
0.4105g, what is the percent by mass of barium in the original unknown compound?
7) An ion containing only oxygen and chlorine is 31%...