Search our library of Chemistry A Level questions

Top answers

Chemistry

A Level

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.

As HCl is a strong acid, it will fully dissociate in water, releasing 1 mmol of H⁺, which will be the final concentration of protons in solution. The autoprotolysis equilibrium of water (or K

Answered by Samuel N. • Chemistry tutor

1564 Views

The reversible reaction of sulfur dioxide and oxygen to form sulfur trioxide is shown below. 2SO2(g) + O2(g) 2SO3(g) An equilibrium mixture contains 2.4mol SO2, 1.2mol O2 and 0.4mol SO3. The total pressure is 250atm. What is the p(SO3)?

First step is to calculate the mole fraction of the SO3. This can be done by dividing the moles of SO3 by the total moles at equilibrium to give 0.4/4. This is then multiplied by the total pressure at equ...

Answered by Saji M. • Chemistry tutor

14495 Views

What are moles and how do you calculate them?

Well this depends whether you require the moles of gas, solid or solution as to which equation you use, moles relate the mass of the atom of interest to that of the number of atoms in 12 grams of carbon-1...

Answered by Benjamin T. • Chemistry tutor

1474 Views

A chemist has 3 beakers, each containing a pure sample of acetone (2-propanone), isopropanol (2-propanol) and propanal. Using chemical techniques, suggest how the chemist may be able to determine which beaker contains which sample. [4]

Brady's reagent is an orange solution of 2,4-dinitrophenylhydrazine which reacts with carbonyl containing functional groups to produce an orange precipitate (2,4-dinitrophenylhydrazone derivative of the c...

Answered by Stephen M. • Chemistry tutor

1737 Views

State and explain the evidence for the delocalisation of electrons in benzene (6 marks)

Benzene does not decolourise bromine water, showing it does not undergo electrophilic addition reactions as the delocalised pi structure is very stable. All of the carbon-carbon bond lengths are the same;...

Answered by Romi A. • Chemistry tutor

2507 Views