Counting Atoms

Front

What is a chemical formula?

Back

A chemical formula is a way of expressing the composition of a substance using symbols for its constituent elements and numbers to indicate the quantity of each element.

Front

What does a subscript in a chemical formula indicate?

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A subscript indicates the number of atoms of the element that are present in a molecule. For example, in H2O, the '2' indicates there are two hydrogen atoms.

Front

What is a coefficient in a chemical formula?

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A coefficient is a number placed in front of a chemical formula to indicate how many molecules or moles of that substance are present. For example, in 2H2O, the '2' indicates there are two molecules of water.

Front

How many atoms of Sodium (Na) are in 6NaCl?

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6

Front

How many elements are in the chemical formula NaHCO3?

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4

Front

What is the difference between a chemical change and a physical change?

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A chemical change results in the formation of new substances, while a physical change does not change the chemical composition of a substance.

Front

What is an example of a physical change?

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Ice melting is an example of a physical change because it changes from solid to liquid without altering its chemical composition.

Front

How many Magnesium (Mg) atoms are in 10MgCl2?

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10

Front

What is the significance of the number in front of a chemical formula?

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The number in front of a chemical formula (coefficient) indicates how many molecules of that compound are present in a reaction.

Front

What does the formula H2O represent?

Back

H2O represents water, consisting of 2 hydrogen atoms and 1 oxygen atom.