Empirical Formulas/% Composition
Stoichiometry
Conversions/Chemical Equations
% Yield/Isotopes
Odds & Ends
100

What is the percent composition of Cu in CuSO4?

63.55/159.65 x 100 = 40%

100

4 NH3  + 5 O2  ---->    4 NO  + 6 H2O

  • If 1 mole of NHis added to an unlimited supply of oxygen, how many moles of nitrogen monoxide, NO, will be produced? 

1 mole of NO

100

Balance this equation:

___Cr  +  ____ O2 ------>  ____ Cr2O3

__4_Cr  +  __3__ O2 ------>  __2__ Cr2O3

100

You have a mixture of the following isotopes with the following percentages and masses. What is the average atomic mass?

75.5 %  Cl-35

24.5%  Cl-37

35.49 amu

100

Name the 7 diatomic elements

HONClBrIF

200

What is the empirical formula of a substance containing 3% H, 32% P, and 65% O?

H3PO4

200

How many grams of iron (III) oxide, Fe2O3, will be produced from the following reaction if you start with 42.84 grams of iron, Fe?

___Fe  + ___ H2O ------>      ___Fe2O3  + ___ H2

61.25 g Fe2O3

200

Balance this equation: 

_ Al2(SO4)3  +  __ Zn(NO3)2----> _Al(NO3)+ _ZnSO4

 Al2(SO4)3  + 3 Zn(NO3)2----> 2 Al(NO3) + 3ZnSO4

200

The average atomic mass of carbon is 12.01 amu.  Carbon has 3 isotopes. C-12, C-13, and C-14.  Which of the three isotopes is most common in nature? Explain.

C-12 because the average atomic mass is a weighted average based on percent abundance.  The most common isotope's mass is closest to the average mass. 

200
  • Determine the number of protons, neutrons, and electrons in each of the following particles.

S-2

Al-28

Al+3

S-2:  p= 16    n= 16        e=18

Al:    p=13    n=15         e=13

Al+3:  p=13    n=14        e=10

300

The empirical formula of a compound is CH.  If the molar mass of this compound is about 78 g, what is its molecular formula?

C6H6

300

How many molecules of sodium chloride, NaCl, will be produced when 5 atoms of sodium, Na, reacts with an excess of chlorine gas?

 2 Na  +  Cl2  ------->          2 NaCl

5 molecules of NaCl

300

Which contains the most atoms of copper?

1 mole of Cu

1 mole of Cu2O

1 molecule of Cu2O

100 grams of Cu

1 mole of Cu2O

300

What are isotopes? Give examples.

Atoms of the same element that differ by their mass or number of neutrons.  

C-12 vs. C-14

H-1 vs. H-2 vs. H-3

300

Name the scientist responsible for each of the following developments.

  • Atomic theory
  • Discovery of electrons
  • Discovery of the nucleus of the atom

Atomic theory:  John Dalton

Electrons:  J.J Thompson

Nucleus:  Ernest Rutherford

400

Tin(II)fluoride is often added to toothpaste as an ingredient to prevent tooth decay.  What is the mass of fluorine in 24.6 g of this compound?  

5.97 g

400

6.0 grams of hydrogen gas, H2, are reacted with 30.0 grams of oxygen gas, O2, to produce water.  

1. Which reagent is in excess? 

2.  How many grams of H2O will be produced?

2 H2   +  O2  ------>      2 H2O

H2 is the excess reagent

33.75 g of water will be produced

400

What substance is the limiting reagent in this equation if 1 mole of Na is reacted with 1 mole of F2?

2 Na  +  F2   ------->       2 NaF

Na - you need 2 moles of Na for every 1 mole of F2

400

You start with 5 grams of CH4 and burn it in the presence of unlimited O2 producing 6 grams of water. What is your percent yield?

CH4  +  2 O2   ------->         CO2  + 2 H2O

Theoretical yield = 11.25 g (stoichiometry)

% yield = 5/11.25 = 44%

400

How many molecules are in 35 g of sodium sulfate?

Molar mass = 142.05 g

1.48 x 1023 molecules

500

The two compounds listed below are fertilizers.
1.   Which of these is the richest source of nitrogen?  

2.  What % of N does it contain?

ammonium nitrate:  NH4NO3

Urea:  (NH2)2CO

Urea - it contains 47% nitrogen.  Ammonium nitrate only contains 35%

500

You react 100 grams of AlCl3 with 50 grams of Ca and produce 100 g of CaCl2.  If your percent yield is 80.1%, what is the theoretical yield of CaCl2?


___Ca  +  ___AlCl3   ------->     __CaCl2  + __ Al

124.8 g of CaCl2

500

What are three quantities that 1 mole equals?

1 mole = molar mass of a compound or element

1 mole = 6.022 x 1023 atoms or molecules

1 mole = 22.4 L 

500

According to pre-lab calculations, a student’s experiment should have produced 2 g of NaCl.  When he weighed his product from lab, only 1.5 g was present.

Determine the following from the data

Theoretical yield?
Actual yield?
% yield?
% error?

Theoretical yield = 2 g
Actual yield = 1.5 g
% yield = 75%  
% error = 25%

500

What is the approximate average atomic mass of this element?  Describe how you calculated this. 

88(.82) + 87(.06) + 86(.10) + 84(.02) =87.66 amu