Sodium Thiosulphate and Hydrochloric Acid

Aim: To investigate how the rate of reaction between Sodium Thiosulphate and Hydrochloric acid is affected by changing the concentration.
THE REACTION: when Sodium Thiosulphate reacts with hydrochloric acid sulphur is produced. The sulphur forms in very small particles and causes the solution to cloud over and turn a yellow colour. This causes the cross to fade and eventually disappear.
Sodium Thiosulphate + Hydrochloric acid »» Sulphur + Sodium Chloride + Sulphur Dioxide + Water
NA2S2O3 + 2HCL »» S + 2NaCl + SO2 + H2O
(aq) + (aq) »» (s) + (aq) + (g) + (l)
PREDICTION: As the concentration of Sodium Thiosulphate increases the length of time for cross to disappear decreases (inverse). This is because the increase of concentration of Sodium Thiosulphate will increase the rate of reaction between Hydrochloric acid and sodium Thiosulphate particles.
SCIENTIFIC REASONS FOR PREDICTION: the results from preliminary experiments support the prediction made.
From the results you can see that there is a directly proportional relationship between the concentration and the rate of reaction. If you increase the concentration then the rate of reaction will also increase.
This experiment is testing how the rate of reaction is affected when concentration is changed. The theory is said that increasing the concentration can increase the rate of reaction by increasing the rate of molecular collisions. The phenomenon behind all of this is the collision theory and how it plays a big role in this investigation. The higher the concentration the less time/faster it will take for the system to turn into equilibrium, and if concentration id decreased, time taken for the solution to go cloudy increases.
Hypothesis: The higher the concentration the faster the rate of reaction will be and the time taken to reach equilibrium will decrease. A more diluted concentration will have a longer rate of reaction and a longer time to reach equilibrium.
Gathered all the apparatus needed for the experiment.
Using a weight balance we measure out 8g of Sodium thiosulphate, that we added too 200cm³ of water. We mixed the solution until all the crystals were dissolved.
Then you pour 50 cm³, 40 cm³, 30 cm³, 20 cm³, and 10 cm³ of the solution into five identical conical flasks. Then you add water to the other conical flasks so that the total volume in each flask in 50 cm³. Make sure to label the flasks so you know which one has so much concentration.
Once that’s done, you must now take a beaker and add 35 cm³ of concentrated Hydrochloric acid to 65 cm³ of water to make a diluted solution.
Now take a piece of paper and draw a black cross on it, and then place one of the flasks on the paper (do one flask at a time). Using a measuring cylinder measure out 5 cm³ of the hydrochloric solution, and add this to the flask. Immediately stir the flask and start the stop watch. One person should do this part.
As soon as you can’t see the cross any more stop the stopwatch, and record the results in a table. Repeat this with all the flasks.

Don't use plagiarized sources. Get Your Custom Essay on
Sodium Thiosulphate and Hydrochloric Acid
Just from $13/Page
Order Essay

Concentration (cm³)

Time (s)

Rate of reaction (s)




40 + water



30 + water



20 + water



10 + water



The rate of reaction is measured by dividing 1 by the time taken for the reaction to take place.
Number of moles of sulphur used: n= m/M
n= 8/32 = 0.25 mols
You can see from the graph that as concentration increases, the time taken for the solution to go cloudy decreases. So the stronger the concentration the faster the rate of reaction is. As the concentration of sodium Thiosulphate decrease the time taken
for the cross to disappear increases, this is an inverse relationship.When equilibrium was reached the solutions turned a yellow color, the stronger the concentration was the higher the turbidity was. When equilibrium was reached SO2 gas and water were released. The more concentrated solution has more molecules, which more collision will occur. So therefore the rate of reaction should depend on how frequently the molecules collide, so more molecules have greater collisions and the reaction happens faster as more products are made in a shorter time. All related to the collision theory.
What we saw what happened was exactly what we expected from the experiment. Our predictions were accurate.
The method we used was fairly accurate, our results weren’t perfect but they were good enough for us to see what happens during the experiment. So overall the results proved the hypothesis and I was able to draw graphs with a line of best fit. In our experiment we keep the HCL a constant, and also keeping the volume of the solution was important to get more accurate results. The results were fairly reliable under our conditions. They could be a bit off from bad measuring, unclean equipment and the timing.
When the concentration of Sodium thiosulphate was increased the rate of reaction increased and the time taken to reach equilibrium decreased, so therefore the rate of reaction is directly proportional to the concentration.
Bibliography: 6 September 2009 9 September 2009

What Will You Get?

We provide professional writing services to help you score straight A’s by submitting custom written assignments that mirror your guidelines.

Premium Quality

Get result-oriented writing and never worry about grades anymore. We follow the highest quality standards to make sure that you get perfect assignments.

Experienced Writers

Our writers have experience in dealing with papers of every educational level. You can surely rely on the expertise of our qualified professionals.

On-Time Delivery

Your deadline is our threshold for success and we take it very seriously. We make sure you receive your papers before your predefined time.

24/7 Customer Support

Someone from our customer support team is always here to respond to your questions. So, hit us up if you have got any ambiguity or concern.

Complete Confidentiality

Sit back and relax while we help you out with writing your papers. We have an ultimate policy for keeping your personal and order-related details a secret.

Authentic Sources

We assure you that your document will be thoroughly checked for plagiarism and grammatical errors as we use highly authentic and licit sources.

Moneyback Guarantee

Still reluctant about placing an order? Our 100% Moneyback Guarantee backs you up on rare occasions where you aren’t satisfied with the writing.

Order Tracking

You don’t have to wait for an update for hours; you can track the progress of your order any time you want. We share the status after each step.


Areas of Expertise

Although you can leverage our expertise for any writing task, we have a knack for creating flawless papers for the following document types.

Areas of Expertise

Although you can leverage our expertise for any writing task, we have a knack for creating flawless papers for the following document types.


Trusted Partner of 9650+ Students for Writing

From brainstorming your paper's outline to perfecting its grammar, we perform every step carefully to make your paper worthy of A grade.

Preferred Writer

Hire your preferred writer anytime. Simply specify if you want your preferred expert to write your paper and we’ll make that happen.

Grammar Check Report

Get an elaborate and authentic grammar check report with your work to have the grammar goodness sealed in your document.

One Page Summary

You can purchase this feature if you want our writers to sum up your paper in the form of a concise and well-articulated summary.

Plagiarism Report

You don’t have to worry about plagiarism anymore. Get a plagiarism report to certify the uniqueness of your work.

Free Features $66FREE

  • Most Qualified Writer $10FREE
  • Plagiarism Scan Report $10FREE
  • Unlimited Revisions $08FREE
  • Paper Formatting $05FREE
  • Cover Page $05FREE
  • Referencing & Bibliography $10FREE
  • Dedicated User Area $08FREE
  • 24/7 Order Tracking $05FREE
  • Periodic Email Alerts $05FREE

Our Services

Join us for the best experience while seeking writing assistance in your college life. A good grade is all you need to boost up your academic excellence and we are all about it.

  • On-time Delivery
  • 24/7 Order Tracking
  • Access to Authentic Sources
Academic Writing

We create perfect papers according to the guidelines.

Professional Editing

We seamlessly edit out errors from your papers.

Thorough Proofreading

We thoroughly read your final draft to identify errors.


Delegate Your Challenging Writing Tasks to Experienced Professionals

Work with ultimate peace of mind because we ensure that your academic work is our responsibility and your grades are a top concern for us!

Check Out Our Sample Work

Dedication. Quality. Commitment. Punctuality

All samples
Essay (any type)
Essay (any type)
The Value of a Nursing Degree
Undergrad. (yrs 3-4)
View this sample

It May Not Be Much, but It’s Honest Work!

Here is what we have achieved so far. These numbers are evidence that we go the extra mile to make your college journey successful.


Happy Clients


Words Written This Week


Ongoing Orders


Customer Satisfaction Rate

Process as Fine as Brewed Coffee

We have the most intuitive and minimalistic process so that you can easily place an order. Just follow a few steps to unlock success.

See How We Helped 9000+ Students Achieve Success


We Analyze Your Problem and Offer Customized Writing

We understand your guidelines first before delivering any writing service. You can discuss your writing needs and we will have them evaluated by our dedicated team.

  • Clear elicitation of your requirements.
  • Customized writing as per your needs.

We Mirror Your Guidelines to Deliver Quality Services

We write your papers in a standardized way. We complete your work in such a way that it turns out to be a perfect description of your guidelines.

  • Proactive analysis of your writing.
  • Active communication to understand requirements.

We Handle Your Writing Tasks to Ensure Excellent Grades

We promise you excellent grades and academic excellence that you always longed for. Our writers stay in touch with you via email.

  • Thorough research and analysis for every order.
  • Deliverance of reliable writing service to improve your grades.
Place an Order Start Chat Now

Order your essay today and save 30% with the discount code Happy