This law states that a compound contains its component elements in a fixed ratio by mass.

• Law of Conservation of Mass

• Law of Definite Proportions

• Law of Conservation of Energy

• Second Law of Thermodynamics

What is the mass percent oxygen in H₂SO_4.

Help: Molar Mass of H₂SO₄ is: 98.

• 65.3%

• 32.5%

• 22.4%

• 57.1%

CuCl2 is a hygroscopic salt (attracts water and forms a hydrate).  A 100 g sample of hydrated CuCl2 was heated to release the water (efflouresce, remember that word?).  After the sample was water free, the remaining sample contained 78.8 g.  How many water molecules were attached to each molecule of CuCl2?

Hint: How many moles of water were vaporized? How many moles of CuCl2 remained?

• 2

• 5

• 1

• 3

Tags

NGSS.HS-PS1-7

How many grams of Iodine are there in 58 grams of PbI₂?

• 31.9

• 38.3

• 26.2

• 40

Tags

NGSS.HS-PS1-7

What is the percent by mass of oxygen in dextrose (C₆H₁₂O₆)?

• 53

• 25

• 33

• 42

The result of a series of experiments determined that a molecule was 30.4% Nitrogen and 69.6% Oxygen by mass. What is the empirical formula of the molecule?

• NO

• N₂O

• NO₂

• N₂O₃

A 28g sample of a compound containing hydrogen, sulfur and oxygen was found to have 0.6 g of Hydrogen, and 18.3 g of Oxygen. What is the percent composition of sulfur for this compound?

• 32.5%

• 65.4%

• 25%

• 21%

Tags

NGSS.HS-PS1-7

LAB SAFETY QUESTION

Chipped or cracked glassware is okay to use.

• True

• False

What is still confusing, how can I help?