Limiting Reactant Practice Notes

Pre-IB Chemistry Topic 1: Limiting Reactant Practice Notes

1. Phosphorus(V) Oxide and Water Reaction

• Chemical Reaction:
    - The equation is given as:
      $P_4O_{10} + 6H_2O <br>ightarrow 4H_3PO_4$

• Problem Statement:
    - A student added 2.20 g of phosphorus(V) oxide ($P_4O_{10}$) to 2.00 g of water ($H_2O$).

• Goal: To calculate the mass of phosphoric acid ($H_3PO_4$) produced.

2. Ammonia and Oxygen Reaction

• Chemical Reaction:
    - The reaction is represented by:
      $4NH_3(g) + 5O_2(g) <br>ightarrow 4NO(g) + 6H_2O(g)$

• Problem Statement:
    - A 2.00 g sample of ammonia ($NH_3$) reacts with 4.00 g of oxygen.

• Goal: To find out how much water ($H_2O$) is produced, in dm³.

3. Sodium and Oxygen Reaction

• Chemical Reaction:
    - Sodium reacts with oxygen to produce sodium oxide ($Na_2O$).

• Problem Statement:
    - 5.00 g of sodium ($Na$) reacts with 5.00 g of oxygen ($O_2$).

• Goal: To determine how many molecules of sodium oxide are produced.

4. Nitrogen and Hydrogen Reaction

• Chemical Reaction:
    - The production of ammonia from nitrogen gas and hydrogen gas:

• Problem Statement:
    - 50.0 g of nitrogen reacts with an excess of hydrogen.

• Goal: To find how many dm³ of ammonia ($NH_3$) are yielded.

5. Iron and Copper(IV) Sulfate Reaction

• Chemical Reaction:
    - The reaction is as follows:
      $2Fe (s) + Cu(SO_4)_2 (aq) <br>ightarrow 2FeSO_4 (aq) + Cu (s)$

• Problem Statement:
    - 3.26 g of iron powder ($Fe$) are added to 0.016 mol of copper(IV) sulfate solution ($Cu(SO_4)_2$).

• Goal: To compute the maximum amount of copper ($Cu$) produced, in grams.

6. Aluminium Sulfate and Calcium Hydroxide Reaction

• Chemical Reaction:
    - The balanced equation is:
      $Al_2(SO_4)_3(aq) + 3Ca(OH)_2(aq) <br>ightarrow 2Al(OH)_3(g) + 3CaSO_4(s)$

• Problem Statement:
    - 34.2 g of aluminium sulfate ($Al_2(SO_4)_3$) reacts with 0.400 mol of calcium hydroxide ($Ca(OH)_2$).
    - Subsequently, several calculations need to be done on the reactants and products.

• Sub-questions:
    - a) Determine how many moles of $Al_2(SO_4)_3$ are present.
      - Options:
        A. 0.0500 mol
        B. 0.100 mol
        C. 0.150 mol
        D. 0.200 mol
    - b) How many moles of $Ca(OH)_2$ remain unreacted after the reaction goes to completion?
      - Options:
        A. 0.400 mol
        B. 0.300 mol
        C. 0.150 mol
        D. 0.100 mol
    - c) Determine the volume that aluminium hydroxide ($Al(OH)_3$) can maximally occupy at standard conditions.
      - Options:
        A. 2.27 dm³
        B. 4.54 dm³
        C. 6.81 dm³
        D. 9.08 dm³

Important Concepts Related to Limiting Reactants

• Limiting Reactant: The reactant that is completely consumed in a reaction, limiting the amount of product formed.

• Excess Reactant: The reactant that remains when the reaction is complete.

• Calculating Moles:
    - The number of moles can be calculated using the formula:
    $ext{Moles} = rac{ ext{Mass (g)}}{ ext{Molar Mass (g/mol)}}$

• Determining Mass of Product:
    - To find the mass of the produced substance, use stoichiometry based on the balanced chemical equation.