Section 2- Elements of Life Flashcards
(3 cards)
What is the trend of group 2 metals reacting with water to produce group 2 metal hydroxides?
The become increasingly more reactive down a group. This is because group 2 metals require to lose 2 electrons to become their stable ions to then formionic attractions with hydroxide ions, and this is more easily done when there is less of an attraction from the positive nucleus. As the atoms become bigger in size, the electron shielding increases, and there is lesser of a attraction between the outer electrons and the central positive nucleus, so barium can lose its electrons very easily, to them form hydroxides with water, whilst berilium doesnt react.
How would you make a soluble salt using a metal?
You would add a metal to an acid (this acid musnt be too strong otherwise the solution will explode). Just choose a suitable metal (i.e. in a metal oxide) and a suitable acid (HCl). Place the metal into a solution of acid and watch it dissolve. Keep adding the metal until it is in excess, you will know this as the metal will not dissolve and it will fall to the bottom. The to obtain dry pure samples of the salt, filter out any excess metal, and crystallise the solution by heating gently to saturate the solution and then remove from the heat to allow the water to naturally evaporate off.
How would you make an insoluble salt using an alkali (soluble base)?
There is no visible end point to this reaction, so you would instead have to do a titration. Add the acid to a solution of alkali and phenolphaline (it will be pink in basic conditions) and titrate the acid in until there is a colour change from pink to colourless. Record the rough titre. Repeat dropwise to obtain a mean concordant result. Then add the volume of acid recorded to alkali to form the neutral salt, but this time without an indicator so as to not contaminate the salt. You can them crystallise the solution in an evaporation basin.
