Hmk. Problem H.3 (Fundamentals)

Moderators: Chem_Mod, Chem_Admin

Samudrala_Vaishnavi 3A
Posts: 93
Joined: Wed Sep 30, 2020 9:34 pm

Hmk. Problem H.3 (Fundamentals)

Postby Samudrala_Vaishnavi 3A » Mon Oct 05, 2020 4:28 pm

Question: The first box below represents the reactants for a chemical reaction and the second box the products that form if all the reactant molecules shown react. Use the following key to write a balanced equation for the reaction. Assume that if two atoms are touching, they are bonded together. Key: oxygen; hydrogen; silicon.

Picture: There is a picture included with this question with two boxes ... l_UN56.png

I was confused with how to even represent this question's equation in the first place in order to balance it, do each of the bonded atoms represent the amount of moles in total? I know box 1 is the reactants and box 2 is the products so am I correct to assume the equation is ?

Benjamin Chen 1H
Posts: 114
Joined: Wed Sep 30, 2020 9:37 pm
Been upvoted: 7 times

Re: Hmk. Problem H.3 (Fundamentals)

Postby Benjamin Chen 1H » Mon Oct 05, 2020 4:33 pm

I believe you are correct. I'm also assuming the picture represents individual atoms, but it can also be inferred to represent the molar ratios because if each conversion from individual molecule to number of moles is just to divide by Avogadro's Number, then the ratios between individual molecules will be conserved in the mole to mole representation because we are just dividing by a constant.

Evie Li_1H
Posts: 95
Joined: Wed Sep 30, 2020 9:48 pm
Been upvoted: 1 time

Re: Hmk. Problem H.3 (Fundamentals)

Postby Evie Li_1H » Mon Oct 05, 2020 4:40 pm

Well since in the products there are two Oxygen atoms per 1 Silicon atom, I assume the full balanced equation would be 2H4Si + 4H2O -> 2SiO2, + 8H2

Posts: 95
Joined: Wed Sep 30, 2020 9:49 pm

Re: Hmk. Problem H.3 (Fundamentals)

Postby JonathanSung_2G » Mon Oct 05, 2020 4:43 pm

The problem gives us a balanced equation in terms of symbols for the elements. On the reactants side, there are 2SiH4 molecules and 4H2O molecules. On the products side, there are 8H2 molecules and 2SiO2 molecules. To double check if the equation is balanced, we can see that there are 2 moles of silicon, 8 moles of hydrogen, and 4 moles of oxygen on each side of the equation. In the image, there are 2 oxygen atoms and 1 silicon atom to make 1 molecule of SiO2 on the products side. Hope this helps!
Last edited by JonathanSung_2G on Mon Oct 05, 2020 4:43 pm, edited 1 time in total.

Melody Wu 2L
Posts: 109
Joined: Wed Sep 30, 2020 10:00 pm
Been upvoted: 1 time

Re: Hmk. Problem H.3 (Fundamentals)

Postby Melody Wu 2L » Mon Oct 05, 2020 4:43 pm

Yes, your answer is correct except the end is actually +8H2.
Each of the bonded atoms make up a molecule or compound. So there's eight sets of 2 hydrogen atoms bonded together--therefore you would have 8 moles of H2 molecules.

Posts: 90
Joined: Wed Sep 30, 2020 9:40 pm

Re: Hmk. Problem H.3 (Fundamentals)

Postby RitaThomas_3G » Tue Oct 06, 2020 9:02 pm

Hey! First, I just wanted to say that yes you are correct in stating that each of the bonded atoms represent the amount of moles in total. This is because the definition of a mole is the "amount of a substance (page F38 of chem textbook)." This means that in the drawing, since there are 2 molecule depictions of H4Si, there would be 2 moles of H4Si. The same would be for all the other molecules as well.

However, in balancing your equation, all of the atoms are correctly balanced except for H. The way that you did it, it shows that there are 16 H atoms from the reactants (8 in H4Si, 8 in H2O), but there are 20 H atoms from the products. This is an easy fix though since there should be 4 less H atoms on the products side, you can just take away 2 (from the 10 moles of H you put) since this would remove 4 H atoms (2 x 2 H atoms = 4 H atoms). This means that the end of the products should say ... + 8H2O.

Isabella Cortes 2H
Posts: 90
Joined: Wed Sep 30, 2020 9:37 pm

Re: Hmk. Problem H.3 (Fundamentals)

Postby Isabella Cortes 2H » Tue Oct 06, 2020 9:26 pm

You were correct in that the bonded molecules a mole of that molecule, however, in the product side of the box there are 8 moles of hydrogen so your balanced equation will be 2H4Si+ 4H2O ---> 2SiO2+ 8H2. I hope that this helps!

Return to “Balancing Chemical Reactions”

Who is online

Users browsing this forum: No registered users and 2 guests