PEREAKSI PEMBATAS

Summary

This video explains how to identify the limiting reagent in a chemical reaction, a key concept in stoichiometry. It walks through the process of determining the limiting reagent by calculating the initial moles of reactants and comparing them based on their coefficients in the balanced equation. Two examples are given, one with NaOH and H₂SO₄, and another with CH₄ and O₂, showing step-by-step how to determine the limiting reagent, the remaining reactant, and the products formed. The video also covers important calculations to determine the amount of leftover reactant and the resulting products, helping students understand how to apply stoichiometry in real chemical reactions.

Takeaways

• 😀 Chemical reactions may not always consume all reactants, and there are different possible outcomes depending on how the reactants behave.
• 😀 In a chemical reaction, reactants can either be fully consumed, partially consumed, or one reactant might be completely used up while the other remains.
• 😀 The reactant that is consumed first is called the limiting reactant or 'pereaksi pembatas'. This concept is crucial for calculating the amount of remaining or produced substances in a reaction.
• 😀 To determine the limiting reactant, you must calculate the initial moles of each reactant and then divide these by their respective coefficients from the balanced equation.
• 😀 The reactant with the smallest value after this calculation is the limiting reactant, which determines how much product is formed and what remains.
• 😀 In the example where NaOH and H2SO4 react, NaOH is the limiting reactant because, after calculation, it has the smallest value compared to H2SO4.
• 😀 For reactions involving mass, you can calculate the initial moles of a substance by dividing its mass by its molecular weight (molar mass).
• 😀 For instance, in the reaction between CH4 and O2, you calculate the moles of CH4 and O2 based on their given masses and molar masses.
• 😀 After determining the limiting reactant, you can calculate the remaining reactant by subtracting the amount used up from the initial amount.
• 😀 In the example with CH4 and O2, CH4 is the limiting reactant, and after the reaction, the remaining O2 is calculated as 0.1 mol, with the products being CO2 and H2O.

Q & A

What is meant by the term 'limiting reactant' in a chemical reaction?

The limiting reactant is the substance that is completely used up first during a chemical reaction, determining the amount of products formed. It is the reactant that runs out before the others.

What are the three possible outcomes when two reactants undergo a chemical reaction?

1. Both reactants are completely used up, forming products. 2. Both reactants remain after the reaction. 3. One reactant is completely used up while the other remains.

How do you determine the limiting reactant in a chemical reaction?

To determine the limiting reactant, you calculate the initial moles of each reactant, divide them by their respective coefficients in the balanced equation, and identify which reactant has the smallest result. The reactant with the smallest value is the limiting reactant.

In the reaction between NaOH and H2SO4, how do you identify the limiting reactant?

In the reaction between NaOH and H2SO4, the molar amounts are compared by dividing the moles of each reactant by their respective coefficients. The smaller result indicates the limiting reactant. In this case, NaOH is the limiting reactant.

Why is it important to identify the limiting reactant in a reaction?

Identifying the limiting reactant is crucial for calculating the amount of products formed, determining the remaining amounts of reactants, and conducting further chemical calculations such as molar volume or concentration.

What steps are involved in determining the limiting reactant from a reaction equation?

First, calculate the initial moles of each reactant. Then, divide each mole value by the coefficient of the reactant in the balanced equation. The reactant with the smallest result is the limiting reactant.

In the second example, how do you calculate the initial moles of CH4 and O2?

For CH4, the molar amount is calculated by dividing the mass (3.2 grams) by the molar mass (16 g/mol), resulting in 0.2 mol. For O2, the molar amount is calculated by dividing the mass (16 grams) by the molar mass (32 g/mol), resulting in 0.5 mol.

What is the role of the mole ratio in determining how much of each reactant reacts?

The mole ratio helps determine the proportions of reactants required to react completely. By using the mole ratio from the balanced equation, you can calculate how much of each reactant is needed or remains after the reaction.

In the example with CH4 and O2, which reactant is the limiting reactant, and why?

CH4 is the limiting reactant because, after dividing the molar amounts by the respective coefficients, the result for CH4 is smaller (0.2 mol) compared to O2 (0.25 mol), indicating that CH4 will be used up first.

How do you calculate the remaining amount of O2 after the reaction with CH4?

To find the remaining O2, subtract the moles of O2 that reacted (0.4 mol) from the initial moles of O2 (0.5 mol). This gives 0.1 mol of O2 remaining.