From the Periodic table, it can be determined that iron (Fe) has an atomic mass of 56 amu, oxygen (O) has an atomic mass of 16 amu, and hydrogen (H) has an atomic mass of 1 amu. What would the atomic mass of Fe(OH)3 be?

73 amu
107 amu
75 amu
219 amu

1 answer

To find the atomic mass of \( \text{Fe(OH)}_3 \), we need to calculate the total mass based on the constituents:

  1. Iron (Fe): The atomic mass of iron is 56 amu.
  2. Oxygen (O): The atomic mass of oxygen is 16 amu.
  3. Hydrogen (H): The atomic mass of hydrogen is 1 amu.

In \( \text{Fe(OH)}_3 \):

  • There is 1 iron atom: \( 1 \times 56 , \text{amu} = 56 , \text{amu} \)
  • There are 3 hydroxide ions (OH), which consist of 1 oxygen and 1 hydrogen:
    • For 3 oxygen atoms: \( 3 \times 16 , \text{amu} = 48 , \text{amu} \)
    • For 3 hydrogen atoms: \( 3 \times 1 , \text{amu} = 3 , \text{amu} \)

Now, sum these values to get the total atomic mass of \( \text{Fe(OH)}_3 \):

\[ \text{Total mass} = \text{mass of Fe} + \text{mass of O (from OH)} + \text{mass of H (from OH)} \] \[ \text{Total mass} = 56 , \text{amu} + 48 , \text{amu} + 3 , \text{amu} = 107 , \text{amu} \]

Thus, the atomic mass of \( \text{Fe(OH)}_3 \) is 107 amu.