SCIENCE - Y10T1 ( precipitation)

• precipitation is the reaction between 2 aqueous solution that forms an insoluble compound
• the SNACAP rule is sodium, nitrate, acetate, calcium hydroxide, ammonium, potassium
• The SNACAP rule do not form precipitates, they are soluble
• ammonium (NH4+),
• group 1 have a valency of +1
• group 2 have a valency of +2
• group 17 have a valency of -1
• hydroxide (OH-)
• sulfate (SO42-)
• nitrate (NO3-)
• carbonate (CO32-).
• the polyatomics are ammonium (NH4+),

  hydroxide (OH-),

  sulfate (SO42-),

  nitrate (NO3-) and

  carbonate (CO32-).
• nitrates form compounds which are always soluble
• chlorides form compounds which are soluble except for silver nitrate
• carbonates form compounds which are usually insoluble
• ion is any atom or group of atoms that bears one or more positive or negative electrical charges
• ionic compound is the compound made by positive and negative ions
• solution is the mixture of solvent and solute
• insoluble is that cannot dissolve in the solvent
• a precipitation reaction is an example of double displacement reaction
• double displacement reaction is when two compound reacts, and the cation and the anion of the two reactants switch places, forming two new compounds or products
• soluble is can dissolve in the solvent
• solvent is liquid in which substance can dissolve
• solute is that substance which can dissolve
• suspension is the mixture of insoluble substance and solvent
• an atom has positive protons in the nucleus and negative electrons surround the nucleus
• the number of protons equals to the number of neutrons, so overall the charge of an atom is neutral
• atoms are more stable if their outer shell is full
• noble gases are extremely stable and non-reactive because their outer shell contains the maximum number of 8 electrons
• the rows - period of the periodic table shows how many shells the atoms have
• the columns in the periodic table shows how many valance electron have in the outer shell ( 1，2，3，-/+4， -3， -2，-1，0）
• when atom loses or gains electrons, it has a charge then becomes an ion
• metals loses electrons to gain stable outer shell which forms positive ion
• non metals gains electrons to gain stable outer shell that forms negative ions
• Nobel gases already have full outer shell which they are unreactive - inert
• the word equation will be : reactant + reactant = product + product
• carbonate is a salt which contain carbonate ion (CO32)
• another neutraliasation formulae - acid + carbonate -> carbon dioxide +water + salt
• we test for coarbon dioxide by using limewater test

  
• carbon dioxide passes through limewater, producing a milky solution due to the precipitation of the insoluble suspension of calcium carbonate