Nov.12 Class

In the beginning of class we reviewed 10-2 questions and everything up to the mole conversion is on the midterm.

molar mass -> g/mol

molar volume -> L/mol -> mL/mol

Example:
A sample of an unknown gas contains 0.0554mol and occupies a volume of 602.0mL. Determine the molar volume.

Percent Mass of Elements in Compunds

Find the % carbon by mass in Glucose. (C6H12O6)
C = 6(12.o) + H = 12(1.0) + O = 6(16.0) = 180 g/mol
% of Carbon = 72g/180g = 0.4 -> 40%
% of Hydrogen = 12g/180g = 0.0666... -> 7%
% of Oxygen = 96g/180g = 0.5333... -> 53%

Percent Composition
- means the % mass of each element in a compound.

Find the composition of NO3
N = 1(14.0) + O = 3(16.0) = 62.0g/mol
% of Nitrogen = 14g/62g = 0.228 -> 23%
% of Oxygen = 48g/62g = 0.77 -> 77%

Finding the mass of an element in a given mass of a compound.

Find the mass of Carbon contained in a 30.0g sample of CO3.
(First find the percent. Then take the percentage as a decimal and multiply it by the given amount.)
C = 1(12.0) + O = 3(16.0) = 60g/mol
% C = 12g/60g = (0.200) (30.0) = 6g
% O = 48g/60g = (0.800)(30.0) = 24g

Find the mass of K,C, and O contained in K2CO3 if the sample is 500.0g
K = 2(39.1) = 78.2 + C = 12 + O = 16(3) = 48 = 138.2g/mol
% of K = 78.2/138.2 = 56.6% -> 0.566(500g) = 283.0g
% of C = 12/ 138.2 = 8.7% -> 0.087(500g) = 43.5g
% of O = 48/138.2 = 34.7% -> 0.347(500g) = 173.5g
Total = 500.0g