Many of the work sheets are designed for teachers to use with their classes. I have therefore password-protected some of the pages that contain answers. To access these pages you need to enter the password, which is a four digit number. The clues to the password are below:

• What is the pH (to 1 significant figure) of a 0.1M solution of ethanoic acid?
• How many isomers are there of C₄H₈ (including E/Z and cyclic)?
• A student was given 2.00 g of a mixture of solid sodium chloride and solid anhydrous magnesium chloride. They dissolved the solid mixture in distilled water and made the solution up to a total volume of 250.0 cm³ in a volumetric flask. They pipetted out 50.00 cm³ of the solution and added excess silver nitrate solution to it. The precipitate was filtered out, dried and weighed. 1.0257 g of silver chloride was obtained.  Determine the amounts in g of sodium chloride and magnesium chloride in the original mixture. Now multiply the mass of sodium chloride by 5 to get a single digit number.
• How many unpaired electrons are there in a transition metal ion that forms a low spin d⁴ octahedral complex ion?

Each of the clues leads to a single digit number – enter them in order when a password is requested. The same password is used throughout this site.