1. © KCL/PENTECH/WCED 2002 Acid indigestion Acid in your stomach sometimes becomes a too concentrated. Indigestion tablets contain an alkali (soluble base), such as sodium hydrogen carbonate (‘bicarb’), which helps neutralise the acidity. Oh Yeah! If an acid reacts with a base it can form a neutral solution containing salt. That is Acid + Base = Salt + Water 1 After supper Ralph complained he had stomach pains. His mum said he probably had too much acid in his stomach. She gave him a Tums tablet. She said it was anti-acid. After an hour he felt much better. DESIGN an experiment for Ralph to test how much acid can be neutralised by one anti-acid tablet. 1 2 3 4 5 6 8 9 10 11 12 13 14 the pH scale more acidicbasic pH 7 is neutral litmus turns red litmus turns blue Remember the pH scale

2. © KCL/PENTECH/WCED 2002 Acid indigestion A drop of blue litmus solution added to tablet 2 Pieces of anti-acid tablets 1. 2. 3. 4. 5. Vinegar added until colour just goes red Red solution 3 cm 10 20 30 40 50 60 70 80 90 100 Measuring volume of acid added DESCRIBE in your own words what is happening in the 5 steps in this experiment. DISCUSS how to improve the experiment. Here are the steps in Ralph’s experiment.

3. © KCL/PENTECH/WCED 2002 Acid indigestion 3 A burette is a special piece of equipment. It makes it easy to measure small volumes of liquid accurately. It is used in neutralisation experiments. A typical burette is made of a long glass tube. The internal diameter of the tube is 12mm. Overall the tube is 740mm long. At the lower end, for about 140mm, the tube narrows to just 3mm diameter. At the very end the glass is drawn to a fine jet. 70 mm from the bottom is a tap that runs across the tube. For 500mm there is a scale that is marked in cm 3. The smallest division on the scale is 0.1cm 3. SKETCH a diagram of a burette.

4. © KCL/PENTECH/WCED 2002 Acid indigestion 4 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 0 10 20 30 40 50 The diagram shows a burette during a neutralisation experiment. From the diagrams RECORD the values of successive readings for the volume of liquid run into the flask. ml

5. © KCL/PENTECH/WCED 2002 Acid indigestion 5 Volume of acid used in cm 3. pH of titre. 2025282930403237 14131172111 These results were obtained using an electronic pH meter. Hydrochloric acid was being run into milk of magnesia. PLOT a graph of the pH against the volume of acid run into the titre. Label the axes carefully. Milk of magnesia can be bought from the pharmacy to cure acid stomach ache.

6. © KCL/PENTECH/WCED 2002 Acid indigestion 14 13 12 11 10 9 8 7 6 5 4 3 2 1 pH of solution Increasing volume of milk of magnesia added 6 pH of solution Milk of magnesia is an alkali which is used to provide relief from too much stomach acid. A student nurse finds this diagram in a book on an experiment where milk of magnesia was added to hydrochloric acid. DESCRIBE what the graph shows using your own words.

7. © KCL/PENTECH/WCED 2002 Acid indigestion Here are some details on laboratory chemicals. NameChemical formulaAcid/alkali Alkali Magnesium hydroxideMg(OH) 2 Alkali Sodium HydroxideNaOHAlkali Sulphuric acidH 2 SO 4 Acid Hydrochloric acidHClAcid Phosphoric acidH 3 PO 4 Acid Aluminium hydroxideAl(OH) 3 AlkaliAmmoniaNH 4 OH Find a periodic table WRITE down at least three patterns you can find in this data. Pattern 1. Pattern 2. Pattern 3. 7

8. © KCL/PENTECH/WCED 2002 Acid indigestion 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH measure of acidity dark red orangegreenbluedark blue light brown dark brown Urine Lemon juice Universal indicator colour Saliva Stomach acid Tomato juice Duodenal fluid Blood A nurse finds this information in a medical book. DESCRIBE the graph in your own words. 8