Stoichiometry

Question 1

Combustion reactions of hydrocarbons balance in what predictable manner?

Answer 1

CxHy + (x+y/4)O2 (g) –> xCO2 (g) + (y/2)H2O (g)

Question 2

Combustion reactions of monosaccharides balance in what predictable manner?

Answer 2

CxH2xOx + xO2 (g) –> xCO2 (g) + xH2O (g)

Question 3

Define the concentration units for molarity, molality, mass percent, and density.

Answer 3

molarity (M) = moles solute per liter solution (mol/L)
molality (m) = moles solute per liter solvent (mol/kg)
mass % = mass solute per mass of solution
density = mass solution per volume solution (g/mL)

Question 4

What steps do you follow to find the empirical formula if the percents of elements are given?

Answer 4

1. Assume a 100 g sample and convert % to gram
2. Covert grams to corresponding moles
3. Divide the mole quantities by the lowest mole quantity

Question 5

What are standard conditions?

Answer 5

1 atm and 298 K

Question 6

What are STP conditions?

Answer 6

1 atm and 273 K

Question 7

What is an important value, concerning volume, when in STP conditions?

Answer 7

One mole of gas occupies 22.4 liters

–> 22.4 L/mol @ 1 atm & 273 K

Question 8

How do you determine the concentration of a solution when diluted?

Answer 8

MV = MV 
(concentration)V = (concentration)V

Question 9

What is a common twist that writers can employ when working with dilution questions?

Answer 9

They could ask for volume added rather than asking for the final total volume.

Question 10

What are the 5 common reactions in chemistry?

Answer 10

1. precipitation rxns (double-displacement rxns)
2. acid-base rxns (neutralization rxns)
3. composition rxns
4. decomposition rxns
5. oxidation-reduction rxns (electron-transfer rxns)