chem

• definition of relative atomic mass is the average mass of one atom of that element when compared to 1/12 the mass of carbon-12 atom
• relative molecular mass refers to the average mass of a molecule of that substance compared to 1/12th the mass of an atom of carbon-12
• relative formular mass refers to the average mass of a unit of an ionic compound when compared to 1/12 the mass of carbon-12 atom
• formula for moles =mass / moles x molar mass
• state the relative mass, relative charge and where it can be found for protons: relative mass: 1 relative charge: +1 where it can be found: nucleus
• state the relative mass, charge and where it can be found for neutrons: relative mass 1, charge 0, found in the nucleus
• state the relative mass, charge and where it can be found for electrons: relative mass: 0 charge: -1 where it can be found: in the electron shell
• formula for neutrons: nucleons - protons
• definition of isotopes; atoms of the same element with same number of protons but different numbers of neutrons
• isotopes has different physical properties due to different number of neutrons and similar chemical properties due to same number of valence electrons
• what can an atom of a different isotope symbol contain?

  different no. of neutrons
• stable electronic configuration: 2.8.8 or 2.8
• definition of anions: gain an electron to be a negative ion
• definition of cations: lose an electron to become positive ion
• ionic bonding: electrostatic attraction between oppositely charged ions
• covalent bonds: sharing of pairs of electrons between two non-metals
• acid contain hydrogen ions (H+) in water
• neutralisation reaction: acid + base = salt + water
• alkali contains OH- ions in water
• compounds have fixed composition
• properties of acids: taste sour, PH levels less than 7 and dissolves in water to conduct electricity
• properties of alkalis: taste bitter, ph level greater than 7 and does not dissolve in water but can be made into solutions that conduct electricity
• test for hydrogen gas: place a lighted splint at mouth of test tube, it will extinguish with a pop sound
• test for co2: bubble the gas into limewater, a white precipitate will form
• test for ammonia gas: place moist red limus paper at mouth of test tube. the litmus paper turns blue
• hydrochloric acid produces metal chloride
• color of methyl orange in acid solution: red
• to reduce acidity of soil, add calcium oxide known as quicklime
• calcium carbonate is used to neutralize acids
• examples of basic oxides: calcium oxide, sodium oxide, magnesium oxide
• basic oxides reacts with acid to form salt and h20
• examples of amphoteric oxide; zinc oxide, aluminium oxides, lead oxide
• amphoteric oxides react with both acid and base
• amphoteric oxides form a colorless solution and is insoluble in h2o
• acid oxides dissolve in h2o to form acidic solution
• neutral oxides are not soluble in water
• carbon dioxide is released when an acid reacts with a metal carbonate
• examples of acidic oxides; nitrogen dioxide, carbon dioxide, sulfur dioxide
• examples of neutral oxides; oxygen, chlorine, bromine, iodine
• air composition of nitrogen; 78%