Why does the pH of neutral water drop when it is left out in an uncovered container on a worktop for a long period of time?
This question tests your knowledge on; the properties of non-metal oxides in solution, the concept of equilibrium, pH.
Non-metal oxides such as (CO2, P4O10, SO2, etc) are acidic in solution. When left out on the worktop, some of the CO2 dissolves in the water to reach the position of equilibium as both the CO2 and H2O are present in high concentrations. As this position of equilibrium is approached, more CO2 overall has dissolved and so the neutral solution has become more acidic. This is due to the concentration of H+ increasing and by using the equation for pH it can be deduced that the pH decreases.
NG
Related Chemistry A Level answers
All answers ▸Explain how the electron pair repulsion theory can be used to deduce the shape of, and the bond angle in, PF3 .
Given the following equilibrium: H2O + H2O <-> H3O+ + OH- and the Kw = 10^-14, determine the concentration of OH- species after the addition of 1 mmol of HCl to 1 L of neutral water.
Write an ionic equation, with state symbols, to show the reaction of calcium with an excess of water.
(i) What property does Magnesium Oxide have that makes it useful to create heat-resistant bricks to line furnaces? (ii) Explain why H2S exists as a gas and H2O exists as a liquid (at r.t.p).