Chemical Equations: Balancing and Ratios
Why do chemical equations have to be balanced?
Because atoms cannot be created or destroyed in a chemical reaction.
Law of conservation of matter!!!
Explain the difference between the actual and theoretical yields in an experiment
Actual is what you get from doing the experiment. Theoretical is what you should have gotten according to the math
If you increase your quantity of an excess reactant, what happens to the amount of product that can be produced?
Nothing would happen since we already have an excess of that product
C2H4 + 3O2 --> 2CO2 + 2H2O
If 3mol of O2 is used, how many moles of H2O will be produced?
2 mole
At home, you decide to make a peanut butter and jelly sandwich.
You use 2 slices of bread, 2 scoops of jelly, and 1 scoop of peanut butter.
What is the ratio of ingredients needed to make this sandwich?
2 : 2 : 1
You perform the following reaction in a chemistry lab:
3K2O + Mg3N2 --> 3MgO + 2K3N
What is your THEORETICAL YIELD of magnesium oxide (in moles) if you start with 3 moles of K2O and 3 moles of Mg3N2?
3 moles
Burgers are made from 2 buns, 1 patty, and 1 slice of cheese.
If I have 4 buns, 7 patties, and 3 slices of cheese, how many burgers can I make? What ingredient is the limiting reactant?
2 burgers
Limited by the amount of buns, so buns are the limiting reactant
4Al + 3O2 --> 2Al2O3
How many moles of aluminum oxide would be produced from 67.67mol of O2?
Bonus: for an extra 100 points, what type of reaction is shown in this equation?
45.11mol of O2
Synthesis or combination reaction
Explain why the mass of all the reactants in a chemical reaction is equal to the mass of all the products
The atoms are balanced and those atoms always have the same molar mass. So, even though the atoms are rearranged into new compounds, the total mass stays the same
What is the equation for percent yield?
Actual Yield / Theoretical Yield * 100 = ____%
N2 + 3H2 --> 2NH3
Given 5.82L of N2 and 27.06L H2, what is the limiting reactant?
N2
5.82L of N2 is 0.26mol and 27.06L of H2 is 1.2mole
We need 3x more H2 than N2 (from the ratio in the chemical reaction), which we have, meaning N2 limits the reaction
HCl + NaOH --> NaCl + H2O
How many grams of water is produced if 4.21mol of hydrogen chloride is used?
Bonus: for an extra 100 points, what type of reaction is shown in this equation?
75.8g of H2O
Double replacement
Balance this chemical equation. Then, identify the ratio of compounds.
FeF2 + N2 --> Fe3N2 + F2
3FeF2 + N2 --> Fe3N2 + 3F2
3 : 1 : 1 : 3
Before a lab, you calculated that should should have ended up with 3.48g of NaCl. After the lab, you actually ended up with 3.38g of NaCl.
Calculate your percent yield
97.1%
2Mg + O2 --> 2MgO
Given 4.8g of Mg and 4.8g O2, what is the limiting reactant?
Mg
4.8g of Mg is 0.20mol and 4.8g of O2 is 0.15mole
We need 2x more Mg than O2 (from the ratio in the chemical reaction), which we do not have, meaning Mg limits the reaction
CaCO3 --> CO2 + CaO
How many grams of calcium carbonate will I need to form 5.87 liters of carbon dioxide?
Bonus: for an extra 100 points, what type of reaction is shown in this equation?
26.23g of CaCO3
Decomposition
Balance this chemical equation. Then, identify the ratio of compounds.
NH3 + O2 --> N2 + H2O
4NH3 + 3O2 --> 2N2 + 6H2O
Before a lab, you calculated that should should have ended up with 0.91 mol of H2O. After the lab, you were left with 14.75g of H2O.
Calculate your percent yield (hint: your actual and theoretical yields need to be in the same unit before you can calculate!)
89.97%
6KBr + Be3N2 --> 2K3N + 3BeBr2
You have 53.5g of KBr and 12.5g of Be3N2
What is the limiting reactant? Based on that, how many moles of BeBr2 could be made?
KBr is limiting reactant
0.225 mol of BeBr2
Zn + 2HCl --> ZnCl2 + H2
If 3.91x1023 particles of Zn is used, how many liters of H2 will be made?
Bonus: for an extra 100 points, what type of reaction is shown in this equation?
14.5L of H2
Single replacement