Phys Sc 436-2006

Pretest 2.1

 

 

1.         Draw appropriate dot structures for the following: Solutions

 

a.         C6H12

b.         OF2

c.         KI

d.         C8(NO2)8          This structure should be the most symmetric possible. It is the world's most powerful chemical explosive.

 

2.         Which of the compounds in #1 are covalent?  (a),(b) and (d) They contain no metals.

 

3.         How many bonds does #1a have?

 

            18                   

 

4.                  Name the following compounds: (for symbols of obscure elements, see footnotes)

 


a.                   OF2______oxygen difluoride___________

 

b.                  KBr____potassium bromide_____________

 

c.                   Ca3P­­2_____calcium phosphide____________

 

d.                  BeCO­3____beryllium carbonate__________

 

e.         MgSO4­­____magnesium sulfate_____________

 

f.          CuS______copper(II) sulfide___________

 

g.                   OsO4______osmium(VIII) oxide___________(use algebra to figure out Os’ charge. Remember oxide is-2 and the sum of all charges in compound is ZERO)

 

h.                   NH4I___ammonium iodide______________

 

i.                     CF­4______carbon tetrafluoride___________

 

j.          Fe(HCO3)2­____iron(II) hydrogen carbonate_____________


 

5.                   Write formulae for the following ionic compounds.( Show work when necessaryL)

 


 

a.                   sodium hydride                          NaH

 

b.                   magnesium nitrate                     Mg(NO3)2

Why? Mg+2 needs two NO3- to create a total charge of ZERO

c.                   copper (II) hydroxide                 Cu(OH)2

d.                   calcium carbonate                     CaCO3

e.                   platinum (IV) chloride                PtCl4

f.                    ammonium chlorate                   NH4ClO3

g.                   diphosphorus pentaselenide        P2Se5

h.                   iridium (III) sulfide                     Ir2S3

6.                   Match the following descriptions with the correct polyatomic ion.

(It has to be one of the eight in your notes. Include charge!)

 

 

a.                   Found in guano and other natural fertilizer, it is needed by plants for the production of amino acids (hint: these contain nitrogen). ______nitrate___________

 

b.                   It'll either knock you out or wake you up with its ammonia-like smell____ammonium_______

 

c.                   Bakers use this to generate carbon dioxide to help puff up their goodies____hydrogen carbonate_______

 

d.                  Get this Cl-containing stuff on your jeans and they'll fade in a hurry!_____chlorate____

 

 

 

 

 

 

 

 


7.         Balance the following:

 

a.         2 Al(s)   +          Fe2O3(s)                        à        Al2O3(s) +          2 Fe(l)

 

b.         4 K      +          O2                                à        2 K2O

 

c.         C3H8    +          5 O2                             à        3 CO2  +          4 H2O

 

d.         3 Ca(NO3)2       +          2 Na3PO4         à        Ca3(PO4)2        +          6 NaNO3

 

e.         CuS     +          2 NaOH                                   à        Cu(OH)2          +          Na2S

 

 

8.         Given:   N2(g) + 3 H­2(g) à2 NH3(g)

 

a.                   What does the little (g) indicate?____gas__________

b.                  What is the minimum number of H­2 molecules needed to react with 10 molecules of N2?____3(10) = 30_________

c.                   If 34 grams of ammonia were produced from 6 grams of hydrogen, how much nitrogen reacted?____28 g_______

d.                  What else is conserved along with mass in any chemical reaction?_____number of atoms_____________

 

 

 

9.         Translate into a chemical equation:

 

Two parts of dihydrogen monoxide liquid decompose to produce gaseous hydrogen and oxygen in a ratio of 2:1.

 

2 H2O(l) à 2 H2(g) +  1 O 2(g)

 

10.       Translate the following into English:

 

a.         2Al(s)   +          Fe2O3(s)            à        Al2O3(s) +          2 Fe(l)

 

2 moles of solid aluminum react with 1 mole of iron(III) oxide to produce 1 mole of solid aluminum oxide and 2 moles of liquid iron

 

b.         2NaCl(aq)          + H2SO4(aq)       à        Na2SO4(aq) +     2HCl

 

2 moles of aqueous sodium chloride react with 1 mole of aqueous hydrogen sulfate(commonly known as sulfuric acid) to produce 1 mole of sodium sulfate and 2 moles of hydrogen chloride, which escapes a s a gas

 

11.       For each element in the following count the number of atoms on each side of the equation:

 

 

Fe2(SO4)3 + 12 KSCN            à        2 K3Fe(SCN)6 + 3 K2SO4

 

 

atom

Left hand side total

Total atoms on right hand side

Fe

2

2(1)= 2

S

3(1) +12 = 15

2(6)(1) + 3(1) = 15

O

12

12

K

12

2(3) + 3(2) = 12

C

12

2(6) = 12

N

12

2(6) = 12

 

 

12.           a. true;                    electronegativity does increase across a period; effective nuclear charge increases

                b. false;                 what’s true: ionization energy in fact increases across a period ;effective nuclear charge increases

                c. false;                 true: the radius decreases across the period. Same number of shells but more protons have squeezing effect.

                d. false;                  true: boiling points and melting points steadily decrease

 

 

 

13.           Which of the following can possibly be the shell diagrams of alkaline earth metals?

 

a.             2e)                                                           b.             2e)1e                      

 

c.             2e)8e)2e                                                 d.             2e)8e)18e)8e)2e

 

Answer ________C_____and   D________                                                 (2 marks; all or nothing)

 

 

 

14.           Explain why H loves to react with another H to form H2. Use dot and shell diagrams in your explanation.        

 

H  .. H      Each hydrogen fills its shell by sharing.

 

 

15.           Which of the following is a characteristic common to both the Thompson and the Rutherford models of the atom? Choose one letter only                                                                        (1 mark)

 

 

A)

 

The atom is made up of positive and negative charges.

 

B)

 

The negative charges are evenly distributed throughout the atom.

 

C)

 

Electrons revolve around the nucleus.

 

D)

 

The nucleus of atoms is made up of protons and neutrons.

 

Answer A

 

16.           Complete the following sentence with a single word.                    (1 mark)

 

 

The mass number, A, of an atom corresponds to the number of particles contained in the atom's nucleus : that is the total number of protons and ________....

 

Neutrons

 

17.           An atom is composed of 23 protons, 23 electrons and 28 neutrons.  Give another isotope for this atom.( 2 marks)

 

 

 This is 51V. Another isotope would be 52V.