HSC Chemistry Assessment Task

Acid Base Titrations 2009

Name ………………………………………………………..

BEFORE USING THE PROGRAM ANSWER QUESTION 1

Question 1. Describe the procedure to prepare your primary standard of a ……………M

Sodium Carbonate solution. List all steps. NOTE You are given a 250ml flask.

Calculation (3 marks)

Procedure (5 Marks)

Log on to your computer and open the Acid / Base titration program.

In the flask select sodium carbonate solution. The Molarity of your sodium carbonate solution

will be …………………………. Moles/Litre and a volume of 20mls

Question 2. What glassware would you use to transfer the Primary standard into your conical flask? What would you use to rinse this glassware?(2 marks)

…………………………………………………………………………………………………………….

Question 3. What liquid would you use to wash your conical flask? Give a reason for your answer.

(3 Marks)

……………………………………………………………………………………………………………………..

……………………………………………………………………………………………………………………..

……………………………………………………………………………………………………………………..

In your burette select Hydrochloric acid solution. Each student will be given an unknown concentration of acid. You must now titrate this acid against your Sodium carbonate solution using methyl orange as your indicator.

UNKNOWN ACID NUMBER = ………………

Perform 3 titrations

Question 4. Record your titre values in a table below and determine your average titre.

(2 marks)

Question 5. a) What were the colour changes for your indicator? …………………………………

(2 marks)

b) At what pH did your indicator change colour? ……………………………………

(1 mark)

c) Could you have used phenolphthalein as your indicator? Explain (3 marks)

…………………………………………………………………………………………….

……………………………………………………………………………………………

Question 5. Calculate the concentration of your unknown acid. Show all working and equations

( 8 marks)

UNKNOWN HCl - Number …………………. was found to have a concentration of

……………………Moles/litre

Question 6 What was the original pH in the conical flask? (1mark) ……………………….

Before titration was thesolution acid or alkaline? ………………………………………

(1 marks)

Give a reason for your answer including relevant equations (3marks)

Answer –

Using the concentration of acid you recorded above. Enter these values into the burette. (make sure you are using HCl)

You have been given an unknown alkali (BASE) solution. In your flask place Sodium hydroxide and for molarity select the unknown below. Use 20mls in the flask and this time use phenolphthalein as your indicator

YOUR UNKNOWN BASE SOLUTION IS NUMBER =

Perform 3 titrations using your standardised acid HCl

Question 7 Record the average titre ……………………………… (1mark)

Print your titration graph

Question 8On your graph indicate

a)the equivalence point. (1mark)

b)The end point. Is there a difference? Explain (3 marks)

c)Give the graph a heading (1mark)

Question 9Calculate the concentration of the unknown base. Show all working and equations. (8 marks)

Question 10 a) What was the pH of your flask after you have added approx 12mls of acid

pH = …………………….

b) Calculate the [H+] in the flask.