Citric acid, C6H8O7 , is present in lemon juice and is classed as a weak acid. 10.00 cm3 of citric acid is reacted with sodium hydroxide, NaOH (aq) , with a concentration of 12.0 g dm-3 to form sodium citrate, Na3C6H5O7 , and water. 32.10 cm3 of sodium hydroxide was required to react with the lemon juice.
A group of students investigated the rate of reaction between sodium thiosulfate and hydrochloric acid by measuring the amount of time taken for a cross marked on a piece of paper to become obscured by a yellow precipitate.
Na2S2O3 (aq) + 2HCl (aq) → 2NaCl (aq) + SO2 (g) + H2O (l) + S (s)
Initially they measured out 15.00 cm3 of 0.900 mol dm-3 hydrochloric acid and then added 40.00 cm3 of 0.0150 mol dm-3 aqueous sodium thiosulfate.
The mark on the paper was obscured 38 seconds after the solutions were mixed.
Their teacher made up 3.00 dm3 of sodium thiosulfate solution using sodium thiosulfate pentahydrate crystals, Na2S2O3•5H2O.
Calculate the required mass, in grams, of these crystals. Give your answer to 2 decimal places.
Using section 2 of the Data booklet, calculate the volume of gas produced, in dm3, in this reaction if it were collected at a temperature of 300 K and 1.00 x 105 Pa.
Using section 2 of the Data booklet determine the volume of phosphine, measured in cm3 at standard temperature and pressure, that was produced. Give your answer to 3 significant figures.
A student carried out an experiment involving a solution of potassium dichromate(VI), K2Cr2O7, with iron(II) sulfate, to find the mass of FeSO4.7H2O in an impure sample, A.
The student recorded the mass of A, dissolved the sample in water and then made the solution up to 500 cm3. After an excess was added, the student found that 25.00 cm3 of this solution reacted with 22.10 cm3 of a 0.020 mol dm–3 solution of K2Cr2O7.
Deduce the full equation for the reaction between acidic Cr2O72- (aq) and Fe2+ (aq) to form Cr3+ (aq)and Fe3+ (aq).
An empty 1.5 dm3 Tupperware container has been kept in the fridge without a lid at 5 °C. The container is removed from the fridge and allowed to reach a temperature of 21 °C. Using your knowledge of Charles's Law, determine the volume of gas, in cm3, that escaped from the container.
A balloon contains 2500 mL of helium gas at a temperature of 75 °C. Determine the new volume in mL of the gas when the temperature changes to 55 °C assuming the pressure is constant. Give your answer to three significant figures.
A 10.0 L container of helium gas with a pressure of 33 000 Pa at 0 °C is heated until the new pressure is 200 000 Pa. Determine the new temperature of the gas assuming the volume remains constant.
