Midterm Exam 2. Practice problems.

 

 

1. For the following binary compounds:

 

a)      Sort compounds on two groups  –

 ionic compounds and molecular compounds (compounds with covalent bonding)

 

b)      Provide formulas for both groups (remember: there are different rules for naming ionic and covalent compounds)

 

 

sodium iodide                         _____________________________________

 

magnesium oxide                    _____________________________________

 

silicon tetrachloride                 _____________________________________

 

sulfur dioxide                          _____________________________________

 

diphosphorus pentoxide          _____________________________________

 

calcium fluoride                      _____________________________________

 

lithium oxide                           _____________________________________

 

carbon tetrafluoride                            _____________________________________

 

 

 

 

 

2. Provide names for the following compounds:

 

a)      Ionic

 

    KI                _____________________________________________

 

CaO                 _____________________________________________

 

MgBr2             _____________________________________________

 

Na2O               _____________________________________________

 

 

 

b)      molecular (covalent)

 

 

SF6                  _____________________________________________

 

P2O5                _____________________________________________

 

NO3                 _____________________________________________

 

N2O5                _____________________________________________

 

 

 

3. Complete following reactions and:

 

a)      Use your knowledge of octet rule to find out the formula of the product. Indicate the charge on each ion (it will help you to decide what subscripts you need for each element).

 

b)      Balance the reaction.

 

 

Na + O2 è

 

 

K2O + H2O è

 

 

Ca + O2 è

 

 

MgO + H2O è

 

 

4. Consider the reaction:

 

2S + 3O2 è 2SO3

 

Following questions are independent from each other

a)How many moles of SO3 will be formed if there are 2.3 moles of O2  and sulfur is present in excess?

 

 

 

 

 

b) How many moles of each reactant (S and O2) do you need to get 6 moles of SO3?

 

 

 

 

 

c) How many grams of SO3 will be formed from 41g of  S if oxygen is in excess?

 

 

 

 

 

d) This reaction was performed with 64 g of S and 64 g of O2.

 

d1)What was the limiting reactant in this case?

 

 

 

d2)What was the theoretical yield?

 

 

 

d3)What was the percent yield if there were 60 g of SO3 collected?

 

 

 

5.Draw a Lewis structure for the molecule of water (H2O), the molecule of methane(CH4), and the molecule of ammonia (NH3). Remember  to obey the octet rule. Mark lone pairs on the Lewis structure.

 

 

6. Write the reaction of oxidation of Na by Cl using a Lewis structure

 

 Na + Cl è NaCl

 

 

 

 

7. True or false:

a) Covalent bondinginvolves the transfer of valence electrons from one atom to another atom

b) in the compounds with ionic bonding elements hold together by Coulombic force.

c)An ionic bond is formed when two atoms share one or more pairs of electrons.

d) When atoms share two electron pairs it is called the double bond.

e) The valence electrons which don’t participate in the covalent bond are called the lone pairs.

 

9. For the following elements : Na, F, Mg, S

 

a) draw the Lewis structure for each element and determine how many electrons should be gained or lost according to the octet rule.

 

d) For each element indicate what kind of ion is formed. (Hint: how do we call a negatively charged ion? a positively charged ion?) Indicate the charge of the ion.

 

10. True or false:

 

a) Ionization energy is the energy required to remove one electron from the atom.

 

b) the atomic radius decreasing when going down a group in the periodic table.

 

c) the elements of the groupVII in the periodic table are metals

 

 

11. Write the formulas of the following compounds.

 

Aluminum sulfate               _________________________________

 

Sodium carbonate                _________________________________

 

Ammonium hydroxide       _________________________________

 

Potassium phosphate          _________________________________

 

 

12. Write the names of the following compounds.

 

K2CO3                         __________________________________

 

NaOH                                    __________________________________

 

KNO3                                     __________________________________

 

MgSO4                        __________________________________