Chemistry Discussion Questions

Chemistry Discussion Question and classmates response:

DQ1 must be 2 paragraphs and classmates response must be 1 paragraph. Must be you own work.

DQ1

What is the significance of a limiting reactant. Discuss how it is found and what it tells us about the amount of product that can be formed. Give a specific example. You need to respond to my questions and to at least three classmates substantially over three days in a manner that furthers the discussion.  Some ideas for responses:             1. Add information that your classmate didn’t include in his/her post.             2. Respond to a classmate’s example.             3. Make up a similar example using a classmate’s information.

Classmate’s responses:

1. The limiting reactant is the reactant that is entirely consumed when a reaction goes to completion” (Ebbing & Gammon, 2013, p. 90). Limited reactant is also known as limiting reagent. The way you would find limited reactant is by looking at the number of moles in each reactant. First, you would determine the balanced chemical equation, second you would convert all information into moles, and last you would calculate the mole ratio for the information that is given to you. You must first identify the order of the limited reactant because you could calculate the percentage yield. With that being said, the reactant in a chemical reaction limits the amount of product that can be formed and this is also known as the limiting reactant. How to identify what reactant is a limited reactant, for example, if you have 1 mole of hydrogen and one mole of oxygen then the limited reactant will be hydrogen. This is due to the balanced equation for making water, we can see that it takes twice as many moles of hydrogen atoms than oxygen atoms to make up water. Furthermore, each oxygen atom requires 2 hydrogen atoms in order to make up water. The hydrogen would run out before oxygen does, and once this happens, the reactant would have to come to an end.

2. The limiting reactant is the reactant that controls the amount of product possible for a process because once the limiting reactant has been consumed, no further reaction can occur. So, the limiting reactant is very important in chemical reactions because it limits the amount of product that can be formed. The reaction will come to an end when all the limiting reactant is consumed. We can calculate the limiting reactant in this way: 1) make sure you have a balanced chemical equation for the chemical reaction 2)convert all given information to moles ( can be done using molar mass as conversion factor) 3)calculate mole ratio (compare actual ratio to calculated ratio) 4)use the amount of limiting reactant to calculate amount of product produced 5)Calculate how much is left in excess of non-limiting reactant (if necessary).

Example: Find the limiting reactant if 78g Na2O2 were reacted with 29.4g H2O

molar mass of Na2O2= Na (22.99)*2=45.98 O(16*2)=32      45.98+32=77.98 g

molar mass of H2O= H (1*2)=2 O=16    2+16=18g

so 78g * (1mol/77.98g)=1.001 mol of Na2O2

and 29.4g * (1mol/18g)=1.633 mol of H2O

given that there are only 1.001 mols of Na2O2, it is the limiting reactant

3. In a chemical reaction, the starting materials are the reactants and the substances formed are the products. In some reactions, one reactant may be used up before the others are depleted. The substance that is used up first is the limiting reactant. In order to find out the limiting reactant you need to look at the part of chemistry that studies amounts of substances that are involved in a reaction. You might be looking at the amounts of substances before the reaction. You might be looking at the amount of material that is produced by the reaction. By finding the limited reactant it helps us achieve our goal of finding out what was left over after the reaction completed.

An example of a limiting reactant is my preparation of French toast. A recipe for French toast requires one egg, 1/2 c of milk, 2 tbsp of oil, and four pieces of bread. On a busy morning, everyone in my family wants French toast. I check my supplies to see how many pieces of French toast I can serve and I find 6 eggs, 4 c of milk, 16 tbsp of oil, and 32 pieces of bread. This tells me that I can only prepare 24 pieces of French toast, six servings, even though I have enough milk, oil, and bread to make more. In this example, the eggs represent the limiting reactant.