Balancing Equations

[Karolina herrera1F]

Can someone explain how you fin out what the net number of moles are? Like after balancing out the equations how do you find the net? Is it 4 because thats the number in front of C4H10?

17. During a summer camping weekend 4 moles of butane (C4H10) gas were used for cooking. Chose the right balanced equation for the combustion of 4 moles of butane gas. What is the net number of moles of gas produced?

A. 4C4H10(g) + 26O2(g) → 16CO2(g) + 20H2O(g); 6

B. 4C4H10(g) + 26O2(g) → 16CO2(g) + 18H2O(g); 4

C. 4C4H10(g) + 25O2(g) → 16CO2(g) + 20H2O(g); 6

D. 4C4H10(g) + 26O2(g) → 16CO2(g) + 20H2O(g); 5

[Chem_Mod]

What the question is asking is the what is the net change of mols of gas. Because all substances are gases, you can just add up the mols of both sides and see how many you gained.

“Net” in this situation is you lost 30 mols of gas(reactants), but produced 34 mols of gas(products), so your “net” gains is 4.

[Karina Vasquez 1D]

What if the substances were different? Would you only add the moles from a particular substance that is asked for?

[Haorui Li 1A]

In this question, it asks "What is the net number of moles of gas produced?", so we look at compounds that are in the gas phase. In the chemical equation, all compounds are in the gas phase, so to calculate the net number, we just calculate the net change from reactants to products. If the questions are asking different states, we should only consider compounds in a particular state.

[somyapanchal1D]

In order to find the net number of moles produced, you have to add up the number of moles on the reactants and products side and then subtract the number of moles on the reactants side from the number of moles on the products side. So, for the first two you would do:

A. (16+20)-(4+26)=6
B. (16+18)-(4+26)=4

The same procedure applies for C and D.

[gabbymaraziti]

Since all reactants and products are in the gaseous form, the problem is simply asking what the net change in total moles is. So, since the reactants amount to 30 moles of gas, and the products amount to 36 moles of gas, your net number of moles produced is 6.

Don't forget to balance the reaction first.