AChoudhry_1L
Posts: 55
Joined: Sat Sep 07, 2019 12:17 am

If a question asks how much of something you will need, should your answer be in grams or moles?

Abigail Menchaca_1H
Posts: 104
Joined: Sat Sep 07, 2019 12:19 am

Would you mind mentioning what the rest of the problem is?

RKopeikin_3L
Posts: 7
Joined: Fri Aug 30, 2019 12:17 am

My guess would be grams but you really need the entire context of the problem to know for sure.

Anna Wu 1H
Posts: 51
Joined: Sat Aug 17, 2019 12:16 am

The question usually specifies what unit you should put your answer in, but the general rule is if the givens are in grams, the answer should be in grams, and if the givens are in moles, the answer should be in moles.

Jamie Lee 1F
Posts: 106
Joined: Fri Aug 09, 2019 12:16 am

The question will usually tell you what it's looking for. However, it definitely helps to "follow the units". For example, when using dimensional analysis and starting with moles, for example, your answer will usually not end up in moles again and typically you'll be looking for grams.

faithkim1L
Posts: 105
Joined: Fri Aug 09, 2019 12:17 am

Usually, the problem will ask for the amount in moles or in grams. When this is not the case, I usually read the context of the problem. In labs, you usually just use grams. It's not very likely that you will use moles in the lab.

LBacker_2E
Posts: 104
Joined: Wed Sep 18, 2019 12:21 am
Been upvoted: 1 time

It will depend on the formulas/equations that are used in the problem. For example, if you are working with molarity, and are asked how much of something you need to get a certain M (mol/L) solution, then your answer would be in moles. But if you are asked to find how much excess reactant in a limiting reactant, you would likely need to calculate that in grams.

Ryan Yee 1J
Posts: 101
Joined: Sat Aug 17, 2019 12:16 am

I'd answer in terms of the given information. However, should the number of grams become very large (say 6-7 digits +) I might convert to kilograms. Moles should always be left either as is, or in scientific notation in my opinion.

Ryan Juncker 3D
Posts: 51
Joined: Wed Sep 18, 2019 12:18 am

It most likely depends on the specific problem, but we were told in discussion today that the general order would be to convert from grams to moles in order to work out the problem; then convert back from moles to grams to show your final answer. The example we used this on today was finding how much carbon dioxide you exhale from taking a 1.35g pill of Salicylic Acid that is 15% SA by weight.

Sally kim 4F
Posts: 53
Joined: Thu Jul 25, 2019 12:17 am

Sometimes it will be in grams, sometimes it will be in moles. It varies depending on what the question is asking. It should be pretty clear in the problem what they are specifically looking for, so don't worry too much!

erica thompson 4I
Posts: 55
Joined: Wed Sep 18, 2019 12:21 am

Like what many people said above, it depends what the problem is asking for. If the problem was asking you to solve for the mass, the answer would be in grams. I believe in lecture today he said that the SI fundamental units were:

- mass = kilograms
- length = meters
- time = seconds

Doreen Liu 4D
Posts: 54
Joined: Wed Sep 11, 2019 12:17 am

You should always answer with the unit that the question is asking. If it began with moles and asked how many moles are in the end, then keep/convert answer into moles, but if it began with grams and asked for the mass, then keep/convert answer into mass.

Luyan Zhang - 2D
Posts: 103
Joined: Sat Jul 20, 2019 12:16 am

If the question asks for "mass", you should put grams

Gabriel Ordonez 2K
Posts: 113
Joined: Sat Jul 20, 2019 12:15 am

Usually, the question will state the required units it wants. Either, it will say, "What is the amount(in moles)..." or "How many grams of x atoms or molecules will be created from x and y," and so on. Please read the question itself and any background passage that precedes it, and you should be able to answer the question to the fullest.

alexfwang3g
Posts: 50
Joined: Thu Jul 11, 2019 12:16 am

Should be specified in the question.

Laurie Tan 4C
Posts: 5
Joined: Thu Jul 11, 2019 12:17 am

The wording in the question should give hints on what units the answer should be in. Since the questions vary so much, it's difficult to pick one unit for all of your answers, so it's best to check what the question is asking for. :)

ValerieChavarin 4F
Posts: 99
Joined: Wed Sep 18, 2019 12:18 am

The question usually specifies which unit is preferred in the answer. If there is a certain question you are referencing, try posting it verbatim, in order to clear up the confusion.

Posts: 102
Joined: Wed Sep 18, 2019 12:21 am

I think you have to look at what the question is asking for in order to determine if the answer should be in grams or moles.

Megan_1F
Posts: 49
Joined: Thu Jul 25, 2019 12:16 am