7/8/2015
Reduce these to proper empirical formulas:
C8H18
______________
Na2C2O4
______________
C7H12
______________
CH3COOH
______________
C6H2CH3(NO2)3
______________
C3H6N3(NO2)3
______________
Practice Problems:
Determine the empirical and molecular formulas for an unknown
compound based on the information provided below:
• Mass Composition Data from Elemental Analysis:
• 51.28 % Carbon
• 9.40 % Hydrogen
• 27.35 % Oxygen
• 11.97 % Nitrogen
• Molar Mass from Mass Spectrometry Data: 234 g/mol
Practice Problems:
Determine the empirical and molecular formulas based on the
information provided below:
• 11.800 grams of an unknown sample containing only C, H, & N
is found to have 7.200 g of carbon, & 4.198 g of nitrogen.
• Molar Mass from Mass Spectrometry Data: 354.3 g/mol
1
7/8/2015
iClicker Participation Question:
Predicting Solubility from Experimental Obsercations
Consider the experimental observations below:
 Reaction 1 forms ppt.: MgCrO4(aq) + KF(aq)
Reaction 2 does not form ppt.: NH4Cl(aq) + NaF(aq)
Reaction 3 does not form ppt: (NH4)2CrO4(aq) + K2SO4(aq)

A. F2CrO4(s)

B. MgK2(s)
C. K2CrO4(s)
Based on these observations, what is the
likely identity of the precipitate
from Observation 1 above?
D. MgF2(s)
E. (NH4)2SO4(s)
Practice Problems:
Write the balanced chemical equations for the reactions below:
• Combustion of butane, C4H10
• Combustion of sucrose, C12H22O11
• Aluminum metal reacts with manganese (IV) oxide to produce
aluminum oxide and manganese metal
• Ammonium phosphate reacts with iron (II) nitrate to produce a
precipitate
• Making potassium nitride from its component elements
• Uranium (VI) fluoride reacts with magnesium metal
Practice Problems:
Write the decomposition for ammonium dichromate to produce
nitrogen gas, water vapor and chromium (III) oxide.
Hint: Dichromate = Cr2O72How many grams of
ammonium dichromate
would be needed to
generate 400. grams of
water from this
decomposition?
2
7/8/2015
Stoichiometry Practice Problems:
Write the balanced chemical equation describing copper (I) oxide
reacting with carbon atoms to form copper metal and carbon dioxide.
• How much copper metal could be produced from 100.0 grams of
copper (I) oxide & 30. grams of carbon?
3