Chem. Lecture 7/26

Define combustion. What does it need to occur, and what does it yield?

Combustion – the process of burning things.


Combustion requires fuel and oxygen to occur.

Produces carbon dioxide and water.


Fuel + O2 (oxygen) → CO2 (carbon dioxide) + H20 (water)

Step-by-step process for determining the


Finding the limiting reactant


1.) Balance the equation

2.) Convert quantities given into mols., if needed

3.) Divide given mols. by stoichiometric coefficient (lowest quotient is the limiting reactant.)

4.) Calculate using given mols of limiting reactant



Symbol, mass, charge, and brief description of what it is


symbol – fish thingie


4 amu (atomic mass units)


+ charge


Ion of Helium, 42He+2



Symbol, mass, charge, brief description




mass = less than 0


(-) NEGATIVE charge



GAMMA (Rays?)


Symbol, mass, charge, brief description



(technically not particles)


Symbol: Upside down fish thingie


No charge



Describe penetrating power of alpha particles
Alpha particles have very weak penetrating power; a sheet of paper will protect from alpha particles
Describe penetrating power of beta particles
Beta particles have a weak-ish penetrating power. They will go through a sheet of paper but metal foil will shield you from beta particles.
Describe penetrating power of gamma “particles”
Gamma ‘particles’ have VERY STRONG penetrating power; it takes inches of lead or a multiple-feet-thick wall of concrete to shield from gamma particles.
Stability of an isotope depends on…
The stability of an isotope depends on the ratio of neutrons to protons
Why is it that neutrons and protons in the nucleus don’t repel each other?
“STRONG FORCE” holds protons together; so that neutrons and protons in the nucleus won’t repel each other.
What is a POSITRON?

A POSITRON is essentially a NEGATIVE-BETA PARTICLE; it is like an electron, except that it has a (+) POSITIVE charge!


0+1 e

What happens to the mass of a substance after each half life?
The mass of a substance is decreased by half every 1/2 life
Which decay/radioactive particle will deflect towards a positively charged plate?
Beta particles will deflect towards a positively charged plate, because beta particles have a negative charge.
Which particle will pass through an electric field undeflected?
Gamma ‘particles’ will pass through an electric field undeflected
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