Calculate concentration of solution

Error

There was an error loading the page.

Contributors

Christian Lawson-Perfect

Feedback

From users who are members of Quantities extension :

Christian Lawson-Perfect

said

Ready to use

5 years, 3 months ago

History

○

Christian Lawson-Perfect 4 years, 9 months ago

Published this.

○

Christian Lawson-Perfect 5 years, 3 months ago

Gave some feedback: Ready to use

○

Christian Lawson-Perfect 6 years, 8 months ago

Gave some feedback: Needs to be tested

○

Christian Lawson-Perfect 6 years, 8 months ago

Created this.

Name	Status	Author	Last Modified
Calculate concentration of solution	Ready to use	Christian Lawson-Perfect	08/07/2020 20:03
Numbas demo: quantities with units	Ready to use	Christian Lawson-Perfect	02/12/2021 15:50

There are 8 other versions that do you not have access to.

Question statement

{amount_acid} of dilute hydrochloric acid is neutralised by {amount_alkali} of {concentration_alkali} sodium hydroxide.

Give any introductory information the student needs.

			Name	Type	Generated Value

amount_acid	quantity	quantity(25, "cm^3")
amount_alkali	quantity	quantity(15, "cm^3")
concentration_alkali	quantity	quantity(0.3, "mol/dm^3")
moles_alkali	quantity	quantity(0.0045, "mol")
reaction_ratio	integer	1
moles_acid	quantity	quantity(0.0045, "mol")
concentration_acid	quantity	quantity(0.18, "mol/dm^3")

Automatically regenerate variables?

Name

Data type

Value

xxxxxxxxxx
 
qty(random(10..40#5),"cm^3")

JME function reference

Description

Describe what this variable represents, and list any assumptions made about its value.

Can an exam override the value of this variable?

Generated value: `quantity`

quantity(25, "cm^3")

→ Used by:

amount_alkali
concentration_acid

This variable doesn't seem to be used anywhere.

Parts

Quantity with units

Quantity with units

Ask the student a question, and give any hints about how they should answer this part.

What was the concentration of the hydrochloric acid?

Help with this part type

Marks

Penalty for revealing steps

Show correct answer on reveal?

Show score feedback icon?

Correct answer

xxxxxxxxxx
 
concentration_acid

The expected quantity.

Input hint

Allow unitless answer?

If not ticked, the student is prevented from submitting an answer without specifying units.

What to do if incompatible units used

If the student's answer is given in units incompatible with the correct answer's units:

"Prevent submission": Prevent the student from submitting until they use compatible units
"Mark as incorrect": Mark the student's answer as incorrect.
"Mark as if correct units used": Mark the student's answer as if they used the correct units, and apply the "different units used" penalty.

What to do if different units used

If the student's answer is given in different units to the expected answer:

"Convert" - silently convert the student's answer to the units used in the correct answer.
"Warn and convert" - show a warning to the student, but convert.
"Prevent submission" - don't allow the student to submit, and show a warning that they must use the same units.
"Mark incorrect" - the student's answer is marked as incorrect.

Penalty if different units used

100%

This penalty is applied if the student gives their answer in different units to the expected answer. The selected percentage of the student's score is taken away.

Margin of error

$10^{ -12 }$

The student's answer is marked correct if the difference between it and the correct answer is at most this value, measured in the same units as the correct answer.

Advice

Since the acid is neutralised, we can conclude that all of it has reacted with the sodium hydroxide.

The equation of the reaction is:

\[ \mathrm{HCl_{(aq)} + NaOH_{(aq)} \rightarrow NaCl_{(aq)} + H_2O_{(l)}} \]

1 mole of $\mathrm{HCl}$ reacts with 1 mole of $\mathrm{NaOH}$, so the number of moles of $\mathrm{HCl}$ must be the same as the number of moles of $\mathrm{NaOH}$.

To work out the number of moles of $\mathrm{NaOH}$, use the formula:

\[ \text{number of moles} = \text{concentration} \times \text{volume} \]

Since the concentration is given in {units_string(concentration_alkali)}, first convert the amount of sodium hydroxide to the same units:

\[ \var{amount_alkali} = \var{amount_alkali in (qty(1,"mol")/concentration_alkali)} \]

Now, the number of moles of $\mathrm{NaOH}$ is:

\begin{align}
\text{number of moles} &= \text{concentration} \times \text{volume} \\
&= \var{concentration_alkali} \times \var{amount_alkali in "dm^3"} \\
&= \var{moles_alkali}
\end{align}

Finally, we can work out the concentration of the hydrochloric acid:

\begin{align}
\text{concentration} &= \frac{\text{number of moles}}{\text{volume}} \\
&= \simplify{{moles_acid}/{amount_acid}} \\
&= \simplify{{moles_acid}/{amount_acid}} \\
&= \var{concentration_acid}
\end{align}

Give a worked solution to the whole question.

Use this tab to check that this question works as expected.

There was an error which means the tests can't run:

Part	Test	Passed?
Quantity with units
Quantity with units		Hasn't run yet
Quantity with units
Quantity with units		Hasn't run yet
Quantity with units
Quantity with units		Hasn't run yet
Quantity with units
Quantity with units		Hasn't run yet
Quantity with units
Quantity with units		Hasn't run yet

This question is used in the following exams:

Quantities extension demo by Christian Lawson-Perfect in Quantities extension.
Grootheden kopie by Johan Maertens in Meetkunde 1e jaar.
Joshua's copy of Quantities extension demo by Joshua Capel in Joshua's workspace.
More advanced demo by Christian Lawson-Perfect in Demos.
Numbas demo by Alan Levine in Alan's workspace.
Engineering demo by Christian Lawson-Perfect in Christian's workspace.
Engineering example by Christian Lawson-Perfect in Christian's workspace.
faisal's copy of Numbas website demo by faisal a in faisal's workspace.
Numbas website demo by Irene Paniccia in Irene's workspace.
Morgiane's copy of Quantities extension demo by Morgiane Richard in Morgiane's workspace.

Loading...

Error

Metadata

Taxonomy: mathcentre

Taxonomy: Kind of activity

Taxonomy: Context

Contributors

Feedback

History

Comment

Checkpoint description

Christian Lawson-Perfect 4 years, 9 months ago

Christian Lawson-Perfect 5 years, 3 months ago

Christian Lawson-Perfect 6 years, 8 months ago

Christian Lawson-Perfect 6 years, 8 months ago

Error in variable testing condition

Error

Warning

Generated value: `quantity`

Parts

Quantity with units

Loading...

Error

Calculate concentration of solution

Metadata

Taxonomy: mathcentre

Taxonomy: Kind of activity

Taxonomy: Context

Contributors

Feedback

History

Comment

Checkpoint description

Christian Lawson-Perfect 4 years, 9 months ago

Christian Lawson-Perfect 5 years, 3 months ago

Christian Lawson-Perfect 6 years, 8 months ago

Christian Lawson-Perfect 6 years, 8 months ago

Error in variable testing condition

Error

Warning

Generated value: quantity

Parts

Quantity with units

Generated value: `quantity`