Chapter 3 Stoichiometry: Calculations with Chemical Formulas and Equations

Calculate the percentage of nitrogen by mass, in Ca(NO3)2.

% N = (2)(14.00)/(164.018) x 100% = 17.1%

Calculate the formula weight of Al(OH)3.

1 Al atom = 1(26.98) = 26.98 amu 3 O atoms = 3(15.99) = 47.97 amu 3 H atoms = 3(1.00) = 3.00 amu = 78.0 amu

Calculate the formula weight for CH3OH.

1 C atom = 1(12.01) = 12.01 amu 4 H atom = 4(1.00) = 4.00 amu 1 O atom = 1(15.99) = 15.99 amu = 32.0 amu

Balance the equations. 1) ___ Fe(s) + ___ O2(g) ---> ___ Fe2O3(s) 2) ___C2H4(g) + ___ O2(g) ---> ___CO2(g) + ___ H2O(g) 3) ___ Al(s) + ___ HCl(aq) ---> ___ AlCl3(aq) + ___ H2(g)

1) 4 Fe(s) + 3 O2(g) ---> 2 Fe2O3(s) 2) C2H4(g) + 3 O2(g) ---> 2 CO2(g) + 2 H2O(g) 3) 2 Al (s) + 6 HCl(aq) ---> 2 AlCl3(aq) + 3 H2(g)

Write a balaced equation for the surface of aluminum metal undergoes a combination reaction with oxygen in the air.

4 Al(s) + 3 O2(g) ---> 2 Al2O3(s)

There are 18 hydrogen atoms and 6 nitrogen atoms. How many NH3 molecules should be shown in the right box keeping respect to the law of conservation of mass?

6 NH3 molecules

Write the balanced equation for the reaction that occurs when ethanol, C2H5OH(l), is burned in air.

C2H5OH(l) + 3 O2(g) ---> 2 CO2(g) + 3 H2O(g)

Write a balanced equation for solid mercury(II) sulfide decomposes into its component elements when heated.

HgS(s) ---> Hg(l) + S(s)