Tutor profile: Perry M.

What process should be used to convert a primary alcohol to an aldehyde?

Primary alcohols can be easily converted to aldehydes by adding an oxidizing agent such as acidified potassium dichromate while heating. However, these are the same conditions that can further oxidize the aldehyde to a carboxylic acid. To isolate the aldehyde before more oxidation can occur, place the reaction in a distillation apparatus. The high boiling point alcohol and any carboxylic acids produced will remain in solution, while the low boiling point aldehyde will evaporate away and can be condensed into a separate container.

Why does atomic size decrease to the right across the periodic table if the atoms are gaining protons, neutrons, and electrons?

An atom's size depends on how tightly its outer electrons are pulled in to the nucleus. Since electrons and protons have opposite charge, the number of protons in the nucleus determines the pull on electrons toward the middle. However, electrons on inner rings also repel outer electrons away, making the atom larger. As you move to the right across the periodic table atoms gain protons which pull electrons in, and electrons are added to the outer ring which only minimally repels other electrons. So, from left to right the increase in pull overcomes electrons repelling each other, making atoms smaller.

Why do acids make pH lower?

pH is a measure of the H+ ions floating around in solution. The more H+, the lower the pH. An acid is a substance that gives off H+ ions when dissolved in water, so it increases H+ concentration, which lowers the pH.