1. A sample of an infusion was diluted 10 ml to 250 ml and then 10 ml to 200 ml. It was then analysed and was found to contain sodium at 0.789 mg/100 ml. Calculate the concentration of sodium in the original sample in %w/v. The sample was composed of a mixture of sodium lactate and sodium carbonate in equimolar amounts. Calculate the amount of sodium lactate and sodium carbonate in mg/10 ml of the sample (Na = 23, lactate = 89, carbonate = 60)
1. A sample of an infusion was diluted 10 ml to 250 ml and then 10 ml to 200 ml. It was then
analysed and was found to contain sodium at 0.789 mg/100 ml. Calculate the concentration
of sodium in the original sample in %w/v. The sample was composed of a mixture of sodium
lactate and sodium carbonate in equimolar amounts. Calculate the amount of sodium
lactate and sodium carbonate in mg/10 ml of the sample (Na = 23, lactate = 89, carbonate =
60)
2. 0.641 g of a semi-synthetic alkaloid was dissolved in 25 ml of 1% w/v acetic acid and was
analysed directly by HPLC. The solution was found to contain 1.42 mg/100 ml of an impurity.
What is the level of impurity in % w/w and ppm?
3. Calculate the pH of a buffer system made by dissolving 1.2 g of acetic acid and 0.82 g of
sodium acetate in 500 ml of distilled water (pKa of acetic acid = 4.7)
4. Convert the following concentrations into the required expression.
| Concentration | given Expression required |
| 0.5% NaCl | molarity |
| 1 mM of KBr | mg/ml |
| 5 mg/100 ml paracetamol | molarity |
| 0.15 N H2SO4 | g/litre |
| 0.5% ethanol/water (w/v) | ppm |
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