We're the Grade 11s in Mr. Doktor's chemistry 11 class.
We're in Block A, Day 1.
We are
Theresa Nguyen
Dominika Skibicki
Charles Perea
Tim Pang
This is our blog.

11/12/09 - DAY 1CDAB
Percent Mass of Elements in Compounds

• Find the % carbon by mass in Ethane (C2H6)
• 2(12g/mol) + 6(1.0g/mol) = 30 g/mol
• % Carbon = 24g/30g = 80.0 %
• % Hydrogen = 6g/30g = 20.0 %

Percent Composition

• Means the % mass of each element in a compound
• Find the % Composition of K2Cr2O7
• 2(39.1g/mol) + 2(52.0g/mol) + 7(16.0g/mol) = 294.2 g/mol
• % K = 78.2/294.2 x 100 = 26.6 %
• % Cr = 104/294.2 x 100 = 35.4 %
• % O = 112/294.2 x 100 = 38.1 %

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

• Find the mass of Carbon combined in a 25.0 g sample of CO2
• % O = 72.2 %
• % C = 27.3 % > (0.273)(25.0g) = 6.82 g

• Find the mass of K,C, and O contained in K2CO3. If the sample is 450.0 g
• 2(39.1g/mol) + 3(16.0g/mol) + 12 = 138.2 g/mol
• % K = 56.6 % > (0.566)(450g) = 250.2 g
• % C = 8.7 % > (0.087)(450g) = 39.15 g
• % O = 34.7 % > (0.347)(450g) = 156.15 g

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