Counting Atoms in Chemical Formulas

• 1

• 2

• 3

• 4

Answer explanation

In one molecule of H₂O (water), there are 2 hydrogen atoms and 1 oxygen atom. Therefore, the correct answer is 2.

Tags

NGSS.MS-PS1-1

• 6

• 12

• 18

• 24

Answer explanation

In the chemical formula C_6H_{12}O_6, the subscript '12' indicates the number of hydrogen atoms. Therefore, the correct answer is 12.

Tags

NGSS.MS-PS1-1

• 3

• 6

• 18

• 23

Answer explanation

In 3Ca(NO3)2, each nitrate (NO3) has 3 oxygen atoms. There are 2 nitrates per formula unit, giving 6 oxygen atoms per unit. With 3 units, the total is 3 x 6 = 18 oxygen atoms.

Tags

NGSS.MS-PS1-1

• 6

• 8

• 9

• 10

Answer explanation

The compound C2H5OH contains 2 carbon (C) atoms, 6 hydrogen (H) atoms, and 1 oxygen (O) atom. Adding these gives 2 + 6 + 1 = 9 total atoms, making the correct answer 9.

Tags

NGSS.MS-PS1-1

• 1

• 2

• 3

• 4

Answer explanation

In the formula Mg(OH)₂, the hydroxide ion (OH) contains one oxygen and one hydrogen atom. Since there are two hydroxide ions, the total number of hydrogen atoms is 2. Therefore, the correct answer is 2.

Tags

NGSS.MS-PS1-1

• 16

• 20

• 24

• 28

Answer explanation

To find the total number of atoms in 2K₃PO₄, calculate: 2(K: 3, P: 1, O: 4) = 2(3+1+4) = 2(8) = 16. However, since there are 2 units, the total is 16. Thus, the correct answer is 24.

Tags

NGSS.MS-PS1-1

• 1

• 2

• 4

• 6

Answer explanation

In the chemical formula H₂SO₄, the subscript '4' indicates there are four oxygen atoms in the molecule. Therefore, the correct answer is 4.

Tags

NGSS.MS-PS1-1

• 1

• 2

• 3

• 4

Answer explanation

In the compound 4NH₃, there are 4 molecules of ammonia (NH₃). Each NH₃ contains 1 nitrogen atom. Therefore, 4NH₃ has 4 nitrogen atoms in total.

Tags

NGSS.MS-PS1-1

• 1

• 2

• 3

• 4

Answer explanation

In the formula Fe₂(SO₄)₃, there are 3 sulfate ions (SO₄) present. Each sulfate ion contains 1 sulfur atom, so 3 sulfate ions contribute a total of 3 sulfur atoms.

Tags

NGSS.MS-PS1-1

• 10

• 15

• 20

• 25

Answer explanation

In 5H₂O, there are 5 water molecules. Each water molecule has 2 hydrogen (H) atoms and 1 oxygen (O) atom, totaling 3 atoms per molecule. Therefore, 5 molecules contain 5 x 3 = 15 atoms, making the correct answer 15.

Tags

NGSS.MS-PS1-1