## Showing Work for Limiting Reactant Calculations on Tests [ENDORSED]

Moderators: Chem_Mod, Chem_Admin

AGaeta_2C
Posts: 112
Joined: Wed Sep 18, 2019 12:21 am

### Showing Work for Limiting Reactant Calculations on Tests

I've seen in lecture we don't really solve limiting reactant problems by using dimensional analysis like we do in discussion. (In lecture we tend to go through the problems step by step). I understand that its essentially the same process and procedure. On tests, will we get full credit if we just show minimal work (dimensional analysis) like we do in discussion?

Chem_Mod
Posts: 18910
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 737 times

### Re: Showing Work for Limiting Reactant Calculations on Tests  [ENDORSED]

Yes

In class I usually go through worked examples step by step using and discussing concepts that assist in understanding and therefore developing a strong foundation.

Anokhi Patel 2B
Posts: 76
Joined: Fri Aug 09, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Yes, I believe we receive credit based on the correct answer, however the step by step problems in lecture are to understand the process of determining the limiting reagent.

SarahCoufal_1k
Posts: 102
Joined: Thu Jul 25, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I don't think you have to show as many steps as in discussion. However, if you mess up the final answer, but show your correct process, you might receive partial credit.

Natalie Benitez 1E
Posts: 100
Joined: Fri Aug 02, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I don't want to be that person but what does dimensional analysis mean?

Ethan Low 1L
Posts: 24
Joined: Wed Sep 18, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I think I remember hearing that if we have the correct answer for tests, even if you did a short cut or mental calculations and skipped a few steps you will still receive credit. However, I think if you do not have the correct final answer but have shown the steps and working that display the proper procedure, we will still get partial credit for the right steps... so it depends on how you want to do it, but it might also make sense to show the steps for formulating your answer in the event of a calculation error.

Catherine Daye 1L
Posts: 104
Joined: Wed Sep 11, 2019 12:16 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I think getting to the correct answer is the most important thing, but work helps the grader understand your line of thought. By showing work, you can also learn from your mistakes, i.e. which step you got confused on.

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

### Re: Showing Work for Limiting Reactant Calculations on Tests

We were told in discussion that all that really mattered on the tests was to get the right answer and we would be given credit; however, If we make a math error early on in the problem and carry that error through but complete the rest of the problem correctly we will be given partial credit. In that case with no work you may not receive the partial credit.

gabbymaraziti
Posts: 111
Joined: Wed Sep 18, 2019 12:19 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Do we need to show our work on tests to show how we calculated the correct number of sig figs? Or is our final answer the only thing we are graded on?

claudia_1h
Posts: 111
Joined: Fri Aug 09, 2019 12:16 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Natalie Benitez 1C wrote:I don't want to be that person but what does dimensional analysis mean?

Dimensional analysis is the process for solving problems where you multiply out the needed ratios (mole/mole, grams/mole, grams/L) and cancel out the units in order to get the correct answer. You know which ratios you need depending on the balanced equation and knowns you are given.

Lauren Sanchez 3D
Posts: 52
Joined: Sat Aug 24, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

My TA also said that an incorrect answer could still receive some partial credit with the correct work/steps, so I think it is a good idea to show work.

AveryAgosto
Posts: 76
Joined: Wed Sep 18, 2019 12:16 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I would recommend showing all of your work regardless of the method you use. For free response tests its always better to show more work for partial credit purposes. I feel like showing that you know the process will be more important and get you more credit than getting the answer correct.

brennayoung
Posts: 51
Joined: Fri Sep 20, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

In my discussion we dont really use dimensional analysis per say so I would think as long as you display some work it would be fine.

KatherineValdez_4B
Posts: 22
Joined: Sat Sep 14, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

So we can get partial credit if we show our work and we have the right idea, but mess up the calculations?

KTran 1I
Posts: 52
Joined: Fri Aug 30, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Is it recommended to just show all of our work when possible? Also, do we need to include the specifications for the element/compound in our calculations?

briannam_1F
Posts: 35
Joined: Wed Sep 18, 2019 12:18 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Are we going to be expected to know how to write the formula for something like "magnesium sulfate heptahydrate," for example, for the test in our discussions? Or will we just be given chemical symbols?

Maya Serota 3G
Posts: 53
Joined: Tue Sep 24, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

briannam_3k wrote:Are we going to be expected to know how to write the formula for something like "magnesium sulfate heptahydrate," for example, for the test in our discussions? Or will we just be given chemical symbols?

I would check with your TA to be completely sure, but the information for the test from Dr. Lavelle says that all equations will be provided. I am also wondering if that includes examples like the one you gave.

Ashley Tran 2I
Posts: 108
Joined: Thu Jul 11, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

briannam_3k wrote:Are we going to be expected to know how to write the formula for something like "magnesium sulfate heptahydrate," for example, for the test in our discussions? Or will we just be given chemical symbols?

Per my discussion with the UA yesterday at the Chem workshop/review session, I was told that we will likely be provided both the compound name and formula. However, you should still know some of the very common compounds in case.

Adelpha Chan 1B
Posts: 58
Joined: Thu Jul 25, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

If the answer is correct, minimal work with dimensional analysis is fine. However, listing out each step makes it easier for you to check your answer and also increases the possibility of partial credit if you make a mistake on a step midway through.

Nare Nazaryan 1F
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Showing work, even if your final answer is incorrect, will always give you partial credit which is important since the tests are 50 points (roughly 7 points/problem if its 7 questions).

Katherine Brenner 3H
Posts: 73
Joined: Wed Sep 18, 2019 12:18 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Hi Nate

Dimensional analysis is the way we solve problems and use the multiplication techniques such as 21 grams 1mole/107 grams and the units cancel out.

TimVintsDis4L
Posts: 104
Joined: Sat Aug 17, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

From what I recall, if you get the answer correct, then you are given full credit as long as some work is shown. However, I would still show work in case I get the problem wrong and my work shown will be worth some partial credit.

Leslie Magana 4C
Posts: 22
Joined: Thu Sep 26, 2019 12:18 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I would show some work just in case but I read that as long as you show some work you'll get partial credit

selatran1h
Posts: 52
Joined: Fri Aug 30, 2019 12:16 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Yes, as long as you follow all of the steps to show the limiting reactant calculations you should receive full credit.

Leila_4G
Posts: 114
Joined: Sat Sep 14, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Do we have to have the formulas of the polyatomic ions memorized?

Angela Prince 1J
Posts: 102
Joined: Sat Aug 24, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Because each question is worth so many points, it would be wise to show at least the basic steps that you used to get to your solution.

BCaballero_4F
Posts: 94
Joined: Wed Nov 14, 2018 12:22 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Yes, however I think it is best to show work so that in case you make a mistake you may receive partial credit.

RichBollini4G
Posts: 100
Joined: Wed Sep 18, 2019 12:18 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

ktran Disc 1I wrote:Is it recommended to just show all of our work when possible? Also, do we need to include the specifications for the element/compound in our calculations?

I think the safe bet is to always show every step with the specifications for an element or compound just in case.

405335722
Posts: 56
Joined: Fri Aug 30, 2019 12:16 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

KatherineValdez_4B wrote:So we can get partial credit if we show our work and we have the right idea, but mess up the calculations?

yes I remember my TA saying we get partial credit for calculations and showing work.

Cassandra_1K
Posts: 49
Joined: Wed Sep 18, 2019 12:16 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

For limiting reactants on the test do we have to explain how we know one is a limiting reactant or can we just specify which one?

Areli C 1L
Posts: 95
Joined: Wed Nov 14, 2018 12:19 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I think it would be best to show your work how you learned it rather than confusing yourself by adding minor steps. However, the minor steps might help you receive partial credit if your answer is incorrect. :)

VioletKo3F
Posts: 103
Joined: Sat Sep 07, 2019 12:18 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Cassandra_1K wrote:For limiting reactants on the test do we have to explain how we know one is a limiting reactant or can we just specify which one?

You should show the work for how you found the limiting reactant. Even if you're wrong, you would be able to get partial credit for explaining.

AveryAgosto
Posts: 76
Joined: Wed Sep 18, 2019 12:16 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

You definitely receive credit for coming to the correct answer but in order to get the most partial credit possible you should write it out step by step.

BSolano_3A
Posts: 7
Joined: Tue Nov 13, 2018 12:18 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

when it comes to answering anything on a test I recommend underlining what it's asking you for and make sure you answer completely. Show full work of what it's asking you, and just that, no need for unnecessary work.

Anvi Brahmbhatt 4A
Posts: 51
Joined: Wed Sep 18, 2019 12:21 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Show as much work as you can when solving the problems on the test in order to receive as much partial credit as you can!

melinak1
Posts: 25
Joined: Tue Sep 24, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

so we do receive partial credit?

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

### Re: Showing Work for Limiting Reactant Calculations on Tests

When in doubt, survival by partial credit! Probably best to show your work so your TA is following along with you during the problem.

MaggieHan1L
Posts: 100
Joined: Thu Jul 11, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Showing your work can also make it easier for you to double check your answers too!

Chetas Holagunda 3H
Posts: 51
Joined: Thu Jul 11, 2019 12:17 am
Been upvoted: 1 time

### Re: Showing Work for Limiting Reactant Calculations on Tests

Showing your work in terms of dimensional analysis also makes it clearer in terms of what factor you need to divide or multiply by.

Celena Kim 2I
Posts: 106
Joined: Sat Sep 14, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Showing work is best because the TA can follow along every step and give you max points for each step.

lauraxie2e
Posts: 108
Joined: Fri Aug 09, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I think it's best to be safe and show all work. However, it really depends on what TA you have.

Madeline Phan 1E
Posts: 103
Joined: Sat Aug 17, 2019 12:18 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I think that you definitely need to show the mole to mole rations for limiting reactant problems on the tests, as those are the key parts of the problem that Dr. Lavelle wants you to understand.

MeeraBhagat
Posts: 95
Joined: Sat Aug 24, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I don't think that every single simple step needs to be shown, but someone who does not know much about chemistry or who would be confused easily should be able to follow along and understand how you got from point A to B.

MeeraBhagat
Posts: 95
Joined: Sat Aug 24, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Cassandra_1K wrote:For limiting reactants on the test do we have to explain how we know one is a limiting reactant or can we just specify which one?

just specify which one

abby hyman
Posts: 60
Joined: Thu Jul 25, 2019 12:16 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

My TA informed us on Monday that if we have the correct answer we get full credit, but if we don't have the correct answer we can get partial credit if the work we've shown is correct but a calculation was messed up

Claire Grover 3G
Posts: 64
Joined: Wed Sep 18, 2019 12:18 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Yes, I believe you will get credit as long as you show your work.

kevinolvera1j
Posts: 103
Joined: Fri Aug 02, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

When showing work it's important to include the right units in your work.

Amy Kumar 1I
Posts: 114
Joined: Thu Jul 11, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I made sure to use dimensional analysis to make it clear when units canceled out.

MBouwman_4A
Posts: 40
Joined: Wed Sep 18, 2019 12:21 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

You don’t have to show as much work. However, it may help so if you make a calculating mistake, graders can see each step and you can get partial credit for completing the steps correctly even with a calculating error.

Tahlia Mullins
Posts: 105
Joined: Thu Jul 25, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

When showing work, I always include units from beginning to end, which makes it easier for the grader to follow as well as serves as a way to check if I got the right answer based on getting down to the right units.

KatherineValdez_4B
Posts: 22
Joined: Sat Sep 14, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I have a question about significant figures. What number do we base the amount of significant figures we use? Like in any problem.

Jose Robles 1D
Posts: 100
Joined: Fri Aug 02, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

KatherineValdez_4B wrote:I have a question about significant figures. What number do we base the amount of significant figures we use? Like in any problem.

Usually we round the sig figs based on those given in the question, seen when numbers are given with excess zeros after decimal(0.500). Try to not round early in the question if possible until the end to preserve accuracy.

AGaeta_2C
Posts: 112
Joined: Wed Sep 18, 2019 12:21 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

KatherineValdez_4B wrote:I have a question about significant figures. What number do we base the amount of significant figures we use? Like in any problem.

You base the number of significant figures of your answer on the least number of significant figures given in the question. For example, given the question, "A solution is prepared by dissolving 55.1g (three sig figs) of KCl in approximately 75mL (two sig figs) of water and then adding water to a final volume of 125mL (three sig figs). What is the molarity of KCl in this solution?"
The answer would be written as 5.9M (two sig figs) because the least number of sig figs in the question is two (look at 75mL)

Sears 4A
Posts: 36
Joined: Tue Feb 05, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

claudia_1e wrote:
Natalie Benitez 1C wrote:I don't want to be that person but what does dimensional analysis mean?

Dimensional analysis is the process for solving problems where you multiply out the needed ratios (mole/mole, grams/mole, grams/L) and cancel out the units in order to get the correct answer. You know which ratios you need depending on the balanced equation and knowns you are given.

This method is also called the Factor Label Method if that is how you are familiar with it

Jared_Yuge
Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

yes as long as you have the correct answer and the grader can tell what you did then you'll get credit

Ruth Glauber 1C
Posts: 100
Joined: Wed Sep 18, 2019 12:20 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I believe partial credit is awarded for steps within the overall problem.

Adelpha Chan 1B
Posts: 58
Joined: Thu Jul 25, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

KatherineValdez_4B wrote:I have a question about significant figures. What number do we base the amount of significant figures we use? Like in any problem.

The amount of significant figures we use is based on the amount of significant figures in the values given in the question.

TimVintsDis4L
Posts: 104
Joined: Sat Aug 17, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I would show all work. I had points taken off my first test for not showing work in some parts. You don't have to show everything step by step, but as long as it shows your calculations you should be fine. If you feel you should have gotten more points for the work you showed you can always talk with the TA's , they're very helpful

KatherineValdez_4B
Posts: 22
Joined: Sat Sep 14, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

When doing any problem, do we have to show the steps for the units?
Like do we have to show how the units change in order to get the final unit?

KatherineValdez_4B
Posts: 22
Joined: Sat Sep 14, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

I'm sorry I realize I might not have made much sense in my last question.

KatherineValdez_4B
Posts: 22
Joined: Sat Sep 14, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

AGaeta_4E wrote:
KatherineValdez_4B wrote:I have a question about significant figures. What number do we base the amount of significant figures we use? Like in any problem.

You base the number of significant figures of your answer on the least number of significant figures given in the question. For example, given the question, "A solution is prepared by dissolving 55.1g (three sig figs) of KCl in approximately 75mL (two sig figs) of water and then adding water to a final volume of 125mL (three sig figs). What is the molarity of KCl in this solution?"
The answer would be written as 5.9M (two sig figs) because the least number of sig figs in the question is two (look at 75mL)

Thank you so much, this was very helpful!

KatherineValdez_4B
Posts: 22
Joined: Sat Sep 14, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

405335722 wrote:
KatherineValdez_4B wrote:So we can get partial credit if we show our work and we have the right idea, but mess up the calculations?

yes I remember my TA saying we get partial credit for calculations and showing work.

Thank you!! Imma need that partial credit.

Jaklin Astvatsatryan
Posts: 91
Joined: Wed Sep 18, 2019 12:18 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

KatherineValdez_4B wrote:
405335722 wrote:
KatherineValdez_4B wrote:So we can get partial credit if we show our work and we have the right idea, but mess up the calculations?

yes I remember my TA saying we get partial credit for calculations and showing work.

Thank you!! Imma need that partial credit.

I messed up on this question because I mixed up my ratio which in turn resulted in me getting the wrong answer so imma talk to my TA too haha thanks

Adelpha Chan 1B
Posts: 58
Joined: Thu Jul 25, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

KatherineValdez_4B wrote:When doing any problem, do we have to show the steps for the units?
Like do we have to show how the units change in order to get the final unit?

I believe you don't have to but showing all the units in your dimensional analysis helps with avoiding mistakes and allows for partial credit to be awarded if you do end up messing up for the final answer.

Varadhan_3G
Posts: 49
Joined: Wed Sep 18, 2019 12:20 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

In addition to showing all units, it would be helpful to clearly split the limiting reaction question into 3 parts: (1) the type of amount for which you are calculating, (2) the dimensional analysis to compare amounts for compounds (3) determination of excess after determining limiting reactant.

Mitchell Koss 4G
Posts: 128
Joined: Sat Jul 20, 2019 12:17 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Only your final answer needs correct units

Ruth Glauber 1C
Posts: 100
Joined: Wed Sep 18, 2019 12:20 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

So do we have to have exact units for each step of the problem, or just correct units for the answer?

bloodorangefield
Posts: 24
Joined: Wed Sep 18, 2019 12:19 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Your final answer needs to have correct sig figs for full points I believe, and I think there is partial credit for longer problems.

Hussain Chharawalla 1G
Posts: 100
Joined: Sat Jul 20, 2019 12:15 am

### Re: Showing Work for Limiting Reactant Calculations on Tests

Only your final answer needs the correct sig fig amount. However, I remember a post that also mentioned for each individual step you only need to round for the final sig fig number. This way, any rounding errors you may have are okay as long as you use the correct number of sig figs as the final answer when rounding in each step.

Return to “Limiting Reactant Calculations”

### Who is online

Users browsing this forum: No registered users and 1 guest