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 the subscript in a chemical formula indicate?

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

Front

What elements are represented in the chemical formula Fe₂O₃?

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Iron (Fe) and Oxygen (O).

Front

How do you calculate the total number of atoms in a chemical formula?

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Add the number of atoms of each element together. For example, in H₂SO₄, there are 2 H, 1 S, and 4 O, totaling 7 atoms.

Front

How many atoms are in the compound H₂O?

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There are 3 atoms in total: 2 hydrogen (H) and 1 oxygen (O).

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What is the total number of atoms in 4H₂O?

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There are 8 hydrogen atoms and 4 oxygen atoms, totaling 12 atoms.

Front

In the formula NaCl, how many sodium (Na) atoms are present?

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There is 1 sodium (Na) atom in NaCl.

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How many sodium (Na) atoms are in 6NaCl?

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There are 6 sodium (Na) atoms in 6NaCl.

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What is the significance of parentheses in chemical formulas like Al₂(SO₄)₃?

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Parentheses indicate that the enclosed group of atoms is a polyatomic ion or a group that is multiplied by the subscript outside the parentheses.

Front

How many oxygen (O) atoms are in Al₂(SO₄)₃?

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There are 12 oxygen (O) atoms in Al₂(SO₄)₃.