Solutions 4

Error

There was an error loading the page.

Contributors

Jamie Antoun

Feedback

From users who are not members of Jamie's workspace :

Christian Lawson-Perfect

said

Ready to use

10 years, 1 month ago

History

○

Christian Lawson-Perfect 7 years, 2 months ago

Published this.

○

Christian Lawson-Perfect 10 years, 1 month ago

Gave some feedback: Ready to use

○

Jamie Antoun 10 years, 10 months ago

Created this.

There is only one version of this question that you have access to.

Question statement

Answer the following question. Please enter your answer as a decimal, not a fraction. Give your answer to 2 decimal places (only round your final answer, use the exact values on your calculator when working out any intermediate steps).

Clicking on 'Show steps' will provide you with some prompts to break down the question into smaller parts.

If you would like to see how to do this question, click on 'Reveal answers' at the bottom of the page.

Give any introductory information the student needs.

			Name	Type	Generated Value

a	integer	3
c	integer	6
b	integer	1

Automatically regenerate variables?

Name

Data type

Value

xxxxxxxxxx
 
random(1..5)

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: `integer`

This variable doesn't seem to be used anywhere.

Parts

Gap-fill
1. Gap Number entry
  Add

Gap-fill

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

$\var{50 * a}$ ml of a $\var{0.25 * b}$ M solution is diluted by adding another $\var{50 * c}$ ml of liquid, what is the new concentration?

Unnamed gap M

Advice

$\var{50 * a}$ ml of a $\var{0.25 * b}$ M solution is diluted by adding another $\var{50 * c}$ ml of liquid, what is the new concentration?

Solution:

We started with $\var{50 * a}$ ml of liquid and added another $\var{50 * c}$ ml so the new volume of liquid is

$\var{50 * a} + \var{50 * c} = \var{50 * (a + c)} \text{ml.}$

$\var{50 * a}$ ml is equal to

$\dfrac{\var{50 * a}}{1000} = \var{50 * a / 1000}\text{L}$

so the number of moles we started with is

$\var{50 * a / 1000} \times \var{0.25 * b} = \var{(50 * a / 1000) * 0.25 * b} \text{ moles}.$

We haven't added any more of the substance so we still have $\var{(50 * a / 1000) * 0.25 * b}$ moles but this is now dissolved in $\var{50 * (a + c)}$ ml of liquid. $\var{50 * (a + c)}$ ml is equal to $\var{50 * (a + c) / 1000}$ L so the new concentration is

$\begin{align} \dfrac{\var{(50 * a / 1000) * 0.25 * b}}{\var{50 * (a + c) / 1000}} & = \var{((50 * a / 1000) * 0.25 * b) / (50 * (a + c) / 1000)} \text{M} \\ & = \var{precround((((50 * a / 1000) * 0.25 * b) / (50 * (a + c) / 1000)), 2)} \text{M to 2 d.p.} \end{align}$

Challenge:

Can you think of a shorter way of doing this calculation? Don't worry if you can't, just go through the steps one by one.

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?
Gap-fill
Gap-fill		Hasn't run yet
Number entry
Number entry		Hasn't run yet
Number entry
Number entry		Hasn't run yet
Number entry
Number entry		Hasn't run yet
Number entry
Number entry		Hasn't run yet
Number entry
Number entry		Hasn't run yet
Number entry
Number entry		Hasn't run yet

This question is used in the following exams:

Loading...

Error

Metadata

Taxonomy: mathcentre

Taxonomy: Kind of activity

Taxonomy: Context

Contributors

Feedback

History

Comment

Checkpoint description

Christian Lawson-Perfect 7 years, 2 months ago

Christian Lawson-Perfect 10 years, 1 month ago

Jamie Antoun 10 years, 10 months ago

Error in variable testing condition

Error

Warning

Generated value: `integer`

Parts

Gap-fill

Loading...

Error

Solutions 4

Metadata

Taxonomy: mathcentre

Taxonomy: Kind of activity

Taxonomy: Context

Contributors

Feedback

History

Comment

Checkpoint description

Christian Lawson-Perfect 7 years, 2 months ago

Christian Lawson-Perfect 10 years, 1 month ago

Jamie Antoun 10 years, 10 months ago

Error in variable testing condition

Error

Warning

Generated value: integer

Parts

Gap-fill

Generated value: `integer`