Chapter 9 review

What does the arrow (->) in a chemical reaction represent

• The direction of gravity

• Separation of atoms

• The conversions of reactants to products

• The flow of electrons

What phase does the abbreviation (aq) indicate?

• Solid

• Liquid

• Gas

• Aqueous

In the reaction 2H2+O2 --> 2H2O, how many hydrogen atoms are on the reactant side?

• 2

• 3

• 4

• 5

Why must chemical equations be balanced?

• To reduce the number of products

• To conserve mass and atoms

• To simplify calculation

• To produce more energy

You are given an unbalanced equation: Fe+ O2 ---> Fe2O3. Describe how you would balance it.

• Add coefficients based on trial and error

• Use only subscripts to balance

• Ignore oxygen atoms

• Add water to neutralize

What unit is used to measure atomic mass?

• Grams

• Kilograms

• Amu

• Moles

The molecular mass of O2 is approximately:

• 12 amu

• 16 amu

• 32 amu

• 44 amu

How is molecular mass determined?

• Multiplying mass by velocity

• Dividing total energy by atom count

• Summing the atomic masses of elements

• Using grams per mole

Why do different masses contain different numbers of molecules?

• Due to temperature

• Because masses vary by element

• Due to phase changes

• Because of light exposure

If a compound has 2 carbon atoms and 6 hydrogen atoms, estimate its molecular mass (C=12 amu, H=1)

• 12 amu

• 18 amu

• 24 amu

• 30 amu