Quiz 1. (40 point) CSUB Chemistry 211 WEB 1/16/98

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1. (10) a) Using the periodic table, find the molar masses of the compounds:

i) Ca(HSO3)2 Calcium bisulfite.

 

ii) Na2S2O3-10 H2O Sodium thiosulfate pentahydrate (See Table 3.5 in text)

 

 

b) Calculate the atomic weight of the unknown element M, if the molar mass of a compound K2MO3 is 138 gm/mol.

 

 

 

 

2. (10) Given the following species: (NH4)+, (C2H3O2)-, Fe(3+), Cl- and(CO3)2-, identify which ones are cations and which ones are anions.

b) Write the appropriate formula and name for the ioniccompounds derived by the combinations,

i) Fe(3+) with Cl-

ii) Fe(3+) with (CO3)2-

iii) (NH4)+ with (C2H3O2)-

iv) (NH4)+ with (CO3)2-

 

3.(15) a) What is the difference between and empirical formula anda molecular formula? Can they ever be the same?

b)Mirex is a pesticide that that is used to control certain agriculturalpests and slowly decomposes in the environment. Mirex is composed of 21.9% carbon and 78.1% chlorine, and its molar mass is 545 gm/mol.

i) Find the empirical formula of mirex.

 

 

 

 

 

ii) What is the molecular formula for the compound?

 

4 (5) How many mols are in each of the following,

a) 100 grams of "coal" = Carbon?

 

 

 

b) 100 grams of water, H2O?