By PSIBERG Team July 10, 2021
Chemical equations must be balanced to equate the number of atoms of reactants and products. As the law of conservation of mass states, “Mass can neither be created nor be destroyed but can be changed from one form to another.” Hence, the total mass of the reactant must be equal to the total mass of the products.
For example,
Na + H2O → NaOH + H2 ( Unbalanced equation )
The total mass of the reactants is 23+18= 41grams whereas the total mass of the products is 40+2=42 grams. This means that this equation needs to be balanced.
2Na + 2H2O → 2NaOH + H2 ( Balanced equation )
Now, the reactants have a total mass of 82grams {(23×2=46) + (18 x 2=36)} and the products formed must have 82grams {(40×2=80) + (2 x 1=2)}.
Rules for Balancing Chemical Equations
- Write reactants and products involved in the reaction correctly.
- Count and write atoms present in reactants and products.
- If carbon is present in your equation, try balancing it first and hydrogen and oxygen at the end.
- Never change the subscripts of atoms to balance the equation.
- Always mention the physical state of the elements and compounds.
Additional links:
- Types of chemical reactions
- Rules for assigning oxidation state
Moderators: Chem_Mod, Chem_Admin
Madelyn Cearlock Posts: 72 Joined: Fri Sep 28, 2018 12:19 am
Postby Madelyn Cearlock » Mon Nov 19, 2018 1:29 pm
For the question that asks why do we balance chemical equations, what was the exact answer that was desired? Thank you!
Christopher Tran 1J Posts: 77 Joined: Fri Sep 28, 2018 12:15 am
Postby Christopher Tran 1J » Mon Nov 19, 2018 1:33 pm
Balancing chemical equations makes sure that the number of moles of reactants and products are the same, and therefore agree with the law of conservation of mass.
Marwan Masri 3B Posts: 31 Joined: Fri Sep 28, 2018 12:23 am
Postby Marwan Masri 3B » Fri Nov 23, 2018 9:39 am
if the number of atoms of each element is not the same on both the reactants and the products side, the law of conservation of mass would be violated.
Kobe_Wright Posts: 83 Joined: Fri Sep 28, 2018 12:16 am
Postby Kobe_Wright » Fri Nov 23, 2018 10:12 am
I put to conserve the law of conservation of mass and I got it right.
Karishma_1G Posts: 67 Joined: Fri Sep 28, 2018 12:18 am
Postby Karishma_1G » Fri Nov 23, 2018 12:05 pm
I said that we balance them because of the law of conservation of mass which states that matter cannot be created nor destroyed.
Xinyi Zeng 4C Posts: 63 Joined: Fri Sep 28, 2018 12:18 am
Postby Xinyi Zeng 4C » Fri Nov 23, 2018 12:23 pm
I wrote "to make sure the law of conservation of mass is obeyed as there should be equal number of atoms of the same element on both sides of the reaction equation", and I got full credit for it. I think the most essential part of the answer is "the law of conservation of mass".
Nathan Mariano 2G Posts: 68 Joined: Fri Sep 28, 2018 12:29 am
Postby Nathan Mariano 2G » Fri Nov 23, 2018 9:43 pm
We balance chemical equations due to the law of conservation of mass, which states that mass can neither be created or destroyed. Therefore, in a chemical reaction, the total mass of the reactants must be equal to the total mass of the products. Balancing equations accounts for the total mass of the reactants and the total mass of the products.
Jack Hewitt 2H Posts: 67 Joined: Fri Sep 28, 2018 12:27 am
Postby Jack Hewitt 2H » Thu Dec 06, 2018 6:25 pm
Madelyn Cearlock wrote:For the question that asks why do we balance chemical equations, what was the exact answer that was desired? Thank you!
Because of the law of conservation of mass.
duenezjuleny1D Posts: 48 Joined: Fri Sep 28, 2018 12:24 am
Postby duenezjuleny1D » Wed Jun 26, 2019 10:55 am
We want to make sure not break the law of conservation of mass. It is important to balance on each side, the products and the reactants.
Brian Kwak 1D Posts: 88 Joined: Fri Sep 28, 2018 12:17 am
Postby Brian Kwak 1D » Wed Jun 26, 2019 11:06 am
It is because of the concept of conservation of mass which states that in an isolated system mass can not be created nor destroyed by chemical reactions or physical transformations. Since the chemical reaction can not destroy or create mass the number of elements from the reactants must equal the number of elements that are produced.
Yasmin Olvera 1D Posts: 29 Joined: Thu Feb 14, 2019 12:15 am
Postby Yasmin Olvera 1D » Sat Jun 29, 2019 10:47 am
To show the conservation of mass. Also my TA said not to assume every chemical equation we get on the exam will be balanced. He said to verify everytime we are presented with an equation to check ourselves that it is balanced.
Karolina herrera1F Posts: 33 Joined: Sat Feb 02, 2019 12:15 am
Postby Karolina herrera1F » Sat Jun 29, 2019 2:29 pm
This would be to show the conservation of mass a chemical equation must have an equal number of each type of atoms on both sides of the reaction arrow.
Joanne Lee 1J Posts: 100 Joined: Thu Jul 25, 2019 12:15 am
Postby Joanne Lee 1J » Wed Oct 02, 2019 1:03 am
According to the law of conservation of mass, during a chemical reaction, mass is neither created or destroyed so the equation must be balanced in order to follow this law.
Return to “Balancing Chemical Reactions”
Jump to
Users browsing this forum: No registered users and 1 guest