Virtual Lab – Chemical Equations
Start the lab by clicking this link.
Login using the provided username. This should bring you to the virtual lab interface. Watch the introduction video and read the directions on the screen.
Record all of your answers in the journal while conducting the entire lab (including the analysis section). DO NOT FORGET TO SAVE YOUR JOURNAL ENTRIES. Upload your saved journal entries here for your grade.
Law of Conservation of Matter
This law states that matter cannot be created or destroyed. This means that during a chemical reaction there are the same number of atoms before and after. However, not all molecules react in a one to one ratio.
Mg + O2 → MgO
Because oxygen is a diatomic molecule (O2) in a one to one ratio, there is an oxygen atom left over that must be used. If we add another atom of magnesium it can bond with that leftover oxygen to produce two molecules of MgO.
2Mg + O2 → 2MgO
This equation is now balanced, meaning that it shows the correct ratio so that there are the same number of atoms before and after the reaction.
When balancing a chemical equation you may NOT change any chemical formulas or add any subscripts.
Steps to Balancing Equations:
Example 1: Balance the following equation.
___CH4 + ___O2 → ___CO2 + ___H2O
C – 1 C – 1
H – 4 H – 2
O – 2 O – 3 (2 + 1)
We can see that our carbons are balanced, but our hydrogen and oxygen atoms are both unbalanced. We may only add coefficients in the underlined spaces. In order to make there be 4 hydrogen on the right side of the equation we should add a 2 in front of H2O.
C – 1 C – 1
H – 4 H – 2
O – 2 O – 3 4
This coefficient balances our hydrogen atoms. It also changes how many oxygen atoms we have on the right side of our equation, so we change our count. Now in order to balance our oxygen atoms we should put a 2 in front of the O2.
C – 1 C – 1
H – 4 H – 2 4
O – 2 4 O – 3 4
Our equation is now balanced!
Balancing is a process of trial and error and you will only get better at it with practice. Also, there are sometimes many paths to the same correct answer. If you find yourself going in circles while balancing a problem, start fresh and don’t get discouraged.
Example 2: Balance the following equation.
___K3PO4 + ___HCl → ___KCl + ___H3PO4
K – 3 K – 1
PO4 – 1 PO4 – 1 We can count this as ONE item because PO4 stays together.
H – 1 H – 3
Cl – 1 Cl – 1
We can see that the K and H are not balanced. We can balance the potassium by putting a 3 in front of KCl.
___K3PO4 + ___HCl → _3_KCl + ___H3PO4
K – 3 K – 1 3
PO4 – 1 PO4 – 1
H – 1 H – 3
Cl – 1 Cl – 1 3
Now we can balance our hydrogen by placing a 3 in front of HCl.
___K3PO4 + _3_HCl → _3_KCl + ___H3PO4
K – 3 K – 1 3
PO4 – 1 PO4 – 1
H – 1 3 H – 3
Cl – 1 3 Cl – 1 3
Now our equation is balanced!
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Click HERE for some more balancing practice. This is not for a grade but will help you gain confidence in your balancing skills!
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