Limiting reagent
- 2. DEFINITION The limiting reactant is a reactant that controls the amount of the product formed in a chemical reaction due to its smaller amount. Limiting reactant Excessive reactant
- 3. EXAMPLE
- 4. • The concept of limiting reactant is analogous to the relationship between the number of “kababs” and the “slices” to prepare “sandwiches”.
- 5. If we have 30 “kababs”
- 6. and ive breads “having 58 slices”,
- 7. then we can only prepare 29 “sandwiches
- 8. One “kabab” will be extra (excess reactant) and “slices” will be the limiting reactant.
- 9. It is a practical problem that we can not purchase exactly sixty “slices” for 30 “kababs” to prepare 30 “sandwiches”.
- 10. EXAMPLE • Consider the reaction between hydrogen and oxygen to form water. 2H2 (g) + O2 (g) 2H2O(l) • When we take 2 moles of hydrogen (4g) and allow it to react with 2 moles of oxygen (64g), then we will get only 2 moles (36 g) of water. Actually, we will get 2 moles (36g) of water because 2 moles (4g) of hydrogen react with 1 mole (32 g) of oxygen according to the balanced equation. Since less hydrogen is present as compared to oxygen, so hydrogen is a limiting reactant. If we would have reacted 4 moles (8g) of hydrogen with 2 moles (64 g) of oxygen, we would have obtained 4 moles (72 g) of water.
- 11. Identification of limiting reactant • To identify a limiting reactant, the following three steps are performed. • 1. Calculate the number of moles from the given amount of reactant. 2. Find out the number of moles of product with the help of a balanced chemical equation. • 3. Identify the reactant which produces the least amount of product as limiting reactant.
- 12. THANKS