Chemistry--balancing equations

Front

A subscript tells

Back

the number of atoms (or group of atoms, if in parentheses).

Front

Coefficients

Back

the large numbers that go in front of a chemical formula; they indicate how many moles or molecules/formula units are present.

Front

Why do we balance equations?

Back

Because the same number of atoms are present before and after a reaction--they are just rearranged.

Front

Which is true of phase notations?

Back

Up arrow means gas product, Down arrow means solid product, Arrows both directions mean reversible reaction, Triangle under arrow means heated reaction

Front

What is notable about the following? F2     H2     N2    Br2    O2     Cl2     I2

Back

They are diatomic molecules. They exist in pairs in nature.

Front

Combustion involves

Back

qualitative data (measuring temperature) and quantitative date (surroundings feel warmer).

Front

How can one prove that carbon dioxide gas is present?

Back

CO2 will react with limewater (calcium hydroxide) to form a calcium carbonate precipitate (chalk).

Front

What role does oxygen play in combustion?

Back

It is a reactant from the air.

Front

Diatomics exist in pairs

Back

when the element is by itself but not necessarily when it is part of a compound

Answer explanation

Think about oxygen. It is a diatomic molecule (O2) when it is by itself, but in the famous compound H2O, it is not in a pair