$Fe_2 O_3+3 H_2 O \rightarrow 2 Fe(OH)_3$
The molar mass of each substance is provided in the table below.
| Substance | Molar Mass (g/mol) |
| :-------------------------------------------------- | :------------- |
| Iron (III) oxide $\left( Fe _2 O _3\right)$ | 159.70 |
| Water $\left( H _2 O \right)$ | 18.02 |
| Iron $($ III $)$ hydroxide $\left( Fe ( OH )_3\right)$ | 106.87 |
How many moles of water are needed?
Answer (1)
Analyze the balanced chemical equation: F e 2 O 3 + 3 H 2 O → 2 F e ( O H ) 3 .
Identify the stoichiometric coefficient for water ( H 2 O ) in the balanced equation.
The stoichiometric coefficient for water is 3.
Therefore, 3 moles of water are needed. 3
Explanation
Analyze the Balanced Equation The balanced chemical equation is given as F e 2 O 3 + 3 H 2 O → 2 F e ( O H ) 3 . We need to determine how many moles of water are needed for the reaction to occur as written.
Determine the Stoichiometric Coefficient From the balanced equation, we can see that 1 mole of iron(III) oxide ( F e 2 O 3 ) reacts with 3 moles of water ( H 2 O ) to produce 2 moles of iron(III) hydroxide ( F e ( O H ) 3 ).
State the Answer Therefore, the number of moles of water needed is simply the stoichiometric coefficient of water in the balanced equation, which is 3.
Examples
In cooking, a balanced chemical equation is like a recipe. If you want to bake a cake (the product), you need specific amounts of ingredients (the reactants). In this problem, we found that you need 3 moles of water for every 1 mole of iron(III) oxide to produce iron(III) hydroxide, just like a recipe tells you how much flour, sugar, and eggs you need. Understanding these ratios ensures you get the desired result, whether it's in a chemical reaction or baking a cake!
