Chemical Formulas Review

Aiden and Avery are discussing chemistry. Aiden asks, 'What are molecules made of?'

• Single atoms

• Multiple atoms bonded together

• Only hydrogen atoms

• Only oxygen atoms

Answer explanation

Molecules are made of multiple atoms bonded together, not just single atoms or atoms of a specific element like hydrogen or oxygen.

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NGSS.MS-PS1-1

Scarlett and Priya are conducting an experiment in their chemistry class. They need to determine how many hydrogen atoms are there in Mg(OH)₂. Can you help them?

• One

• Two

• Three

• Four

Answer explanation

To determine the number of hydrogen atoms in Mg(OH)₂, we look at the formula. There are 2 hydrogen atoms in each hydroxide group (OH), and Mg(OH)₂ has 2 hydroxide groups, so there are a total of 2 * 2 = 4 hydrogen atoms. Therefore, the correct answer is Two.

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In Scarlett's science project, she used the molecule Na₂CO₃. How many oxygen (O) atoms are there in this molecule?

• One

• Two

• Three

• Four

Answer explanation

The molecule Na₂CO₃ contains three oxygen (O) atoms. Each CO₃ group has one oxygen atom, totaling three in the molecule.

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NGSS.MS-PS1-1

Ava is learning about water molecules in her science class. In the molecule H₂O, how many oxygen (O) atoms are there?

• One

• Two

• Three

• Four

Answer explanation

In the water molecule H₂O, there is one oxygen (O) atom. The formula H₂O indicates one oxygen atom bonded to two hydrogen atoms.

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Samuel and Elijah are working on a chemistry project. They need to determine the number of oxygen atoms in the molecule 4 Pb(NO₃)₂. How many oxygen atoms are present?

• 4

• 8

• 12

• 24

Answer explanation

To find the number of oxygen atoms in 4 Pb(NO₃)₂, we multiply the number of oxygen atoms in one NO₃ group (3) by the coefficient in front of the group (2) and then by the total number of NO₃ groups (4). Therefore, 3 * 2 * 4 = 24 oxygen atoms.

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Charlotte has 3 molecules of water (H₂O). How many hydrogen (H) atoms are present in total?

• 2

• 3

• 4

• 6

Answer explanation

Each water molecule (H₂O) has 2 hydrogen atoms. With 3 molecules, the total hydrogen atoms are 3 x 2 = 6. Therefore, there are 6 hydrogen atoms in total.

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Lily is conducting a chemistry experiment and needs to know the number of oxygen atoms in the formula Mg(OH)₂. How many oxygen atoms are there?

• 1

• 2

• 3

• 4

Answer explanation

The formula Mg(OH)₂ contains 2 oxygen atoms. The subscript '2' after the OH group indicates there are 2 oxygen atoms in the formula.

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Arjun and Anika are working on a chemistry project. Based on the formula 2 CO₂, how many carbon atoms are there?

• 1

• 2

• 3

• 4

Answer explanation

Based on the formula 2 CO₂, there are 2 carbon atoms present. The coefficient '2' indicates the number of carbon atoms.

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In a chemistry experiment, Olivia and Benjamin are analyzing the molecule 4 Pb₃(PO₄)₂. How many lead (Pb) atoms are there in the molecule?

• 3

• 6

• 9

• 12

Answer explanation

To find the number of lead (Pb) atoms in the molecule, we look at the subscript next to Pb, which is 3. Since there are 4 Pb₃ groups, the total number of Pb atoms is 4 x 3 = 12.

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William and Mia are conducting an experiment with sulfuric acid (H₂SO₄). If they have 2 molecules of H₂SO₄, how many sulfur (S) atoms are there?

• 1

• 2

• 3

• 4

Answer explanation

Each molecule of H₂SO₄ contains 1 sulfur (S) atom. With 2 molecules, there are a total of 2 sulfur atoms.

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