What is the main difference between H2O and H2O2?

• H2O has one hydrogen atom, H2O2 has two.

• H2O has two oxygen atoms, H2O2 has one.

• H2O is water, H2O2 is hydrogen peroxide.

• H2O is safe to drink, H2O2 is not.

What does a chemical formula tell us?

• The color of a substance.

• The elements and their proportions in a substance.

• The temperature at which a substance melts.

• The taste of a substance.

In the chemical formula H2O, what does the subscript '2' indicate?

• Two oxygen atoms.

• Two hydrogen atoms.

• Two water molecules.

• Two elements.

In the formula CO2, what does the subscript '2' apply to?

• Oxygen

• Carbon

• Both carbon and oxygen

• Neither carbon nor oxygen

What does the subscript outside the parentheses in Ca(OH)2 indicate?

• Two oxygen atoms

• Two hydrogen atoms

• Two hydroxide units

• Two calcium atoms

How many hydrogen atoms are in two molecules of NH3?

• 6

• 9

• 3

• 12

What does a whole number coefficient in front of a chemical formula apply to?

• Everything in the formula

• Only the last element

• Only the elements in parentheses

• Only the first element

If the chemical formula is 2C12H22O11, how many carbon atoms are there?

• 12

• 22

• 24

• 44

In the formula 2Ca3(PO4)2, how many phosphorus atoms are there?

• 8

• 6

• 4

• 2

What is the best way to count atoms in a complex formula?

• Count all atoms first, then ignore the coefficient.

• Ignore the leading coefficient first, then count atoms and distribute the coefficient.

• Distribute the coefficient first, then count atoms.

• Count atoms randomly.