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Today we will:
Today we will:Learn about
Elements and Compounds.
HOMEWORK:
Read section 3.4Answer questions 20-24 on page 76.
An element is a pure substance that cannot be broken down by physical or chemical means.
Elements and Compounds
An element is a pure substance that cannot be broken down by physical or chemical means.
Elements and Compounds
A compound is two or more elements combined chemically.
Elements and Compounds
A compound is two or more elements combined chemically.
Elements and Compounds
Law of definite proportions:
Elements and Compounds
Law of definite proportions:A compound always has the same elements in the same proportions by mass.
Elements and Compounds
Law of multiple proportions:
Elements and Compounds
Law of multiple proportions:Some elements combine in several different proportions, but always in ratios of small whole numbers.
Elements and Compounds
Sample Problems
% = x 100
Sample Problems
partwhole
A 20.0g sample of sucrose contains:
8.44g Carbon1.30g Hydrogen10.26g Oxygen
What is the percent by mass of each element in the compound?
Sample Problems
A 20.0g sample of sucrose contains:
8.44g Carbon1.30g Hydrogen10.26g Oxygen
What is the percent by mass of each element in the compound?
Sample Problems
8.44g C
Sample Problems
1.30g H
10.26g O
8.44g C 20 g
Sample Problems
1.30g H 20 g
10.26g O 20 g
8.44g C 20 g
Sample Problems
1.30g H 20 g
10.26g O 20 g
x 100 %
x 100 %
x 100 %
8.44g C 20 g
Sample Problems
1.30g H 20 g
10.26g O 20 g
x 100 % = 42.2 % C
x 100 %
x 100 %
8.44g C 20 g
Sample Problems
1.30g H 20 g
10.26g O 20 g
x 100 % = 42.2 % C
x 100 % = 6.5 % H
x 100 %
8.44g C 20 g
Sample Problems
1.30g H 20 g
10.26g O 20 g
x 100 % = 42.2 % C
x 100 % = 6.5 % H
x 100 % = 51.3 % O
8.44g C 20 g
Sample Problems
1.30g H 20 g
10.26g O 20 g
x 100 % = 42.2 % C
x 100 % = 6.5 % H
x 100 % = 51.3 % O
8.44g C 20 g
Sample Problems
1.30g H 20 g
10.26g O 20 g
x 100 % = 42.2 % C
x 100 % = 6.5 % H
x 100 % = 51.3 % O 100 %
Two unknown compounds are tested. Compound I contains 64.20g of copper and 35.80g of chlorine. Compound II contains 47.27g of copper and 52.73g of chlorine. Are the compounds the same?
Sample Problems
Two unknown compounds are tested. Compound I contains 64.20g of copper and 35.80g of chlorine. Compound II contains 47.27g of copper and 52.73g of chlorine. Are the compounds the same?
Sample Problems
64.20g Cu35.80g Cl
47.27g Cu52.73g Cl
Sample Problems
64.20g Cu35.80g Cl
47.27g Cu52.73g Cl
Sample Problems
=
=
64.20g Cu35.80g Cl
47.27g Cu52.73g Cl
Sample Problems
= 1.793
=
64.20g Cu35.80g Cl
47.27g Cu52.73g Cl
Sample Problems
= 1.793
= 0.8964
64.20g Cu35.80g Cl
47.27g Cu52.73g Cl
Sample Problems
= 1.793
= 0.8964
=
64.20g Cu35.80g Cl
47.27g Cu52.73g Cl
Sample Problems
= 1.793
= 0.8964
= 2
HOMEWORK:
Read section 3.4Answer questions 20-24 on page 76
.