FC 024 Wednesday 02/03/16
2 – 4pm
Enthalpy of neutralisation
(Working in Pairs)
Define the enthalpy of neutralisation
Write a balanced equation for the reaction of hydrofluoric acid and sodium hydroxide. Is this reaction exothermic or endothermic?
100cm3of 1M hydrofluoric acid at 20°C added to 100cm3 of 1M sodium hydroxide at 20°C produced a maximum temperature of 28°C for the mixture. Calculate ΔH.
*specific heat capacity of the solution (C) is 4.2 Jg-1K-1
When an acid neutralises a base, a salt and water are formed. Aqueous hydrogen ions (H+(aq)) from the acid react with the hydroxide ions (OH–(aq)) from the base forming water, e.g.
H+Cl– + Na+OH– → Na+Cl– + H2O
The Na+ and Cl– ions remain unchanged; the only reaction is between the H+ and OH– ions:
H+ (aq) + OH– (aq) → H2O (l)
The neutralisation reaction will occur when H+ and OH– combine and energy is released until either H+ or OH– is entirely consumed. The reactant which is consumed first is called the limiting reactant.
The molar enthalpy of neutralization is defined as
Where qneut is the heat of neutralization, and n is the moles of the limiting reactant.
qneut = c m ∆T
Where m is the mass of solution
C is the specific heat capacity of the solution = 4.2 Jg-1K-1
∆T is the temperature difference
In this practical, we shall be measuring the enthalpy changes (ΔH) for different neutralisation reactions. Because the number of moles of water formed varies according to the acids and bases used, it is the convention to measure enthalpies of neutralisation (ΔH) in kilojoules per mole of water formed.
Experiment 1: The reaction between Hydrochloric acid and sodium hydroxide
Measure 50cm3 of 2.0M hydrochloric acid into a polystyrene cup placed in a beaker and records its temperature. Pour 50cm3 2.0M sodium hydroxide into a measuring cylinder and record the temperature. Pour the sodium hydroxide into the acid, stir and take the final temperature.
(Note: if the acid and base were not at the same temperature initially, use the average of their initial temperature as the starting temperature)
Repeat experiment 1 using 2.0M potassium hydroxide solution instead of sodium hydroxide solution.
Repeat experiment 1 using 2.0M nitric acid (caution – corrosive) instead of the hydrochloric acid.
Repeat experiment 1 using 2.0M sulphuric acid instead of the hydrochloric acid.
Repeat experiment 1 using 2.0M sulphuric acid and 4.0M sodium hydroxide
Repeat experiment 1 using 4.0M sodium hydroxide solution.
Table of Results
Initial temp. 0C
Final temp. 0C
Treatment of results
Write a balanced equation for each experiment including the states.
How much energy (qneut) was given to the 100cm3 of final solution during the reaction? (Assume that the specific heat capacity of the plastic cup is negligible and the specific heat capacity of the solution is 4.2 Jg-1K-1
How many mole of water was formed in each reaction (show your calculation).
Calculate the enthalpy change of neutralisation for each reaction (you’re your calculation).
Accepted values for the enthalpy changes of neutralisation of some acids and bases are shown below.
HCl + NaOH → NaCl + H2O
HNO3 + NaOH → NaNO3 + H2O
HBr + NaOH → NaBr + H2O
CH3COOH + NaOH → CH3COONa + H2O
Compare the experimental values to the values in the table for the first two reactions. Account for any errors in your results.
Why is the enthalpy change for ethanoic acid slightly lower than the values for the first three reactions? (Hydrochloric, nitric and hydrobromic acids are all strong acids. Ka (ethanoic acid) =1.7×10-5.
Compare the temperature rise when 4.0M sodium hydroxide is used instead of 2.0M. Explain the relative values.
Experiment 4: Enthalpy of Neutralisation
Behaviour in the lab.(respect of safety, focus, Attendance) 3
Write-up and quality of report 10
Treatment of results
Balanced equation for each reaction 6
Energy for each reaction 6
Moles of water in each reaction. 6
Calculate the enthalpy changes for each reaction 6
Q 5 3
Observation, Discussion and Conclusion 6
Our Service Charter
Excellent Quality / 100% Plagiarism-FreeWe employ a number of measures to ensure top quality essays. The papers go through a system of quality control prior to delivery. We run plagiarism checks on each paper to ensure that they will be 100% plagiarism-free. So, only clean copies hit customers’ emails. We also never resell the papers completed by our writers. So, once it is checked using a plagiarism checker, the paper will be unique. Speaking of the academic writing standards, we will stick to the assignment brief given by the customer and assign the perfect writer. By saying “the perfect writer” we mean the one having an academic degree in the customer’s study field and positive feedback from other customers.
Free RevisionsWe keep the quality bar of all papers high. But in case you need some extra brilliance to the paper, here’s what to do. First of all, you can choose a top writer. It means that we will assign an expert with a degree in your subject. And secondly, you can rely on our editing services. Our editors will revise your papers, checking whether or not they comply with high standards of academic writing. In addition, editing entails adjusting content if it’s off the topic, adding more sources, refining the language style, and making sure the referencing style is followed.
Confidentiality / 100% No DisclosureWe make sure that clients’ personal data remains confidential and is not exploited for any purposes beyond those related to our services. We only ask you to provide us with the information that is required to produce the paper according to your writing needs. Please note that the payment info is protected as well. Feel free to refer to the support team for more information about our payment methods. The fact that you used our service is kept secret due to the advanced security standards. So, you can be sure that no one will find out that you got a paper from our writing service.
Money Back GuaranteeIf the writer doesn’t address all the questions on your assignment brief or the delivered paper appears to be off the topic, you can ask for a refund. Or, if it is applicable, you can opt in for free revision within 14-30 days, depending on your paper’s length. The revision or refund request should be sent within 14 days after delivery. The customer gets 100% money-back in case they haven't downloaded the paper. All approved refunds will be returned to the customer’s credit card or Bonus Balance in a form of store credit. Take a note that we will send an extra compensation if the customers goes with a store credit.
24/7 Customer SupportWe have a support team working 24/7 ready to give your issue concerning the order their immediate attention. If you have any questions about the ordering process, communication with the writer, payment options, feel free to join live chat. Be sure to get a fast response. They can also give you the exact price quote, taking into account the timing, desired academic level of the paper, and the number of pages.