Chemistry: Atomic Mass, Concentration, Formulas, Ions, Acids, Bases, Reactions, Exams of Nursing

Download Chemistry: Atomic Mass, Concentration, Formulas, Ions, Acids, Bases, Reactions and more Exams Nursing in PDF only on Docsity! AS LEVEL OCR CHEMISTRY EXAM QUESTIONS AND ANSWERS GRADED A+ Isotopes - answer-Different atomic forms of the same element. Atoms with the same number of protons but a different number of neutrons Relative atomic mass - answer-The mean mass of an atom of an element, compared to 1/12th of the mass of an atom of carbon-12 Concentration= - answer-Number of moles ÷ Volume One mole - answer-6.02×10^23 Number of moles= - answer-mass ÷ molar mass r.t.p - answer-25 ºC 100 kPa (1 atm) Molar gas volume - answer-24 dm³ / mol One mole of any gas always has the same volume at r.t.p Number of moles= - answer-Volume (dm^3) ÷ Molar gas volume (24 dm^3 / mol) R- Gas constant - answer-8.314 J / K / mol Gas equation - answer-pV = nRT (Pa)(m³)(K) Assumes forces between molecules are negligible and the molecules have a negligible size Empirical formula - answer-The smallest whole number ratio of atoms of each element in a compound Molecular formula - answer-The actual number of atoms of each element in a compound Ions: Nitrate Carbonate Sulfate Hydroxide Ammonium Zinc ion Silver ion - answer-Formula: NO3- CO3²- SO4²- OH- NH4+ Zn²+ Ag+ Acids - answer-Proton donors - produce H+ ions in water Alkalis - answer-Proton acceptors - produce OH- ions in water Acid + Base= Metal oxide + Acid= Metal hydroxide + Acid= - answer-Salt + Water Metal + Acid= - answer-Metal salt + Hydrogen Metal carbonate + Acid= - answer-Metal salt + Carbon dioxide + Water Bond angle- 104.5º Trigonal bipyramidal - answer-5 electron pairs around central atom No lone pairs Bond angle- 120º, 90º Octahedral - answer-6 electron pairs around central atom No lone pairs Bond angle- All 90º Electronegativity - answer-An atom's ability to attract the electron pair in a covalent bond Three types of intermolecular forces - answer-Induced dipole-dipole Permanent dipole-dipole interactions Hydrogen bonding Induced dipole-dipole - answer-All atoms and molecules are attracted Permanent dipole-dipole interactions - answer-Weak electrostatic forces of attraction between polar molecules Hydrogen bonding - answer-Only possible when hydrogen is bonded to fluorine, nitrogen or oxygen Periodic table blocks - answer- First ionisation energy - answer-The energy needed to remove one mole of electrons from one mole of gaseous atoms Factors affecting ionisation energy - answer-Nuclear charge Atomic radius Shielding Ionisation energy drop between groups 2 and 3 is due to sub-shell structure - answer-The outer electron in group 3 elements is in a p orbital rather than an s orbital. A p orbital has a slightly higher energy than an s orbital in the same shell so the electron is further from the nucleus. The p orbital has additional shielding provided by the s electrons which override the effect of increased nuclear charge. Ionisation energy drop between groups 5 and 6 is due to p orbital repulsion - answer-The repulsion between two electrons in a p orbital in group 6 elements means they are easier to remove than a singly- occupied p orbital in group 5 elements. Carbon allotropes- high melting and boiling points, also insoluble - answer-Diamond- Each carbon atom is covalently bonded to four other carbon atoms in a tetrahedral shape. Silicon also forms a crystal lattice structure with similar properties as each silicon atom can form four covalent bond Graphite- Each carbon atom forms three covalent bonds so there is one delocalised outer electron Graphene- One layer of graphite in a hexagonal sheet, one atom thick. Transparent and incredibly light in one layer Halogens (25ºC): Fluorine- gas Chlorine- gas Bromine- liquid Iodine- solid - answer-Colour: Pale yellow Green Red-brown Grey Test for halides - answer-Silver nitrate solution First add dilute nitric acid Silver halides - answer-Silver chloride- White precipitate, dissolves in ammonia Silver bromide- Cream precipitate, dissolves in concentrated ammonia Silver iodide- Yellow precipitate, insoluble in concentrated ammonia Disporportionation - answer-The same element is both oxidised and reduced Halogen + alkali ----> X2 + 2NaOH ----> Disproportionation reaction - answer-Metal halogen-ate + Metal salt + Water NaXO + NaX + H2O Chlorine and sodium hydroxide make bleach, Sodium chlorate(I) - answer-2NaOH + Cl2 ----> NaClO + NaCl + H2O 0 +1 -1 Chlorine + Water ↔ Cl2 + H2O ↔ - answer-Hydrochloric acid + Chloric(I) acid HCl + HClO Chloric(I) acid + Water ↔ HClO + H2O ↔ - answer-Chlorate ion + Hydronium ClO- + H3O+ Chlorate ions kill bacteria Homologous series - answer-Same general formulas and functional groups Carbon skeleteon - answer-Aromatic or aliphatic Aromatic compounds contain a benzene ring Aliphatic compounds contain carbon and hydrogen joined in straight chains, branched chains or non- aromatic rings (alicyclic) Isomers - answer-Same molecular formula but different structural formula, the atoms are arranged differently Types- Structural isomers and stereoisomers Structural isomers - answer-Chain isomers- The carbon skeleton can be arranged differently (straight or branched) Similar chemical properties but different physical properties Positional isomers- The functional group could be attached to a different carbon atom different physical and maybe chemical properties Functional group isomers- The same atoms can be arranged into different functional groups Very different physical and chemical properties Alkane molecule shape - answer-Alkane molecules are tetrahedral around each carbon atom Each carbon atom has four pairs of bonding electrons around it Bond angle- 109.5º Halogen + Alkane= - answer-Haloalkane (photochemical reaction) Free-radical substitution reaction 1) Initiation- Free radicals are produced 2) Propagation- Free radicals are used up and created 3) Termination- Free radicals are mopped up Alkene double bond - answer-Sigma bond- Two s orbitals overlap, C-C or C-H in alkanes (high bond enthalpy) Pi bond- Sideways overlap of two adjacent p orbitals (low bond enthalpy) E/Z isomerism - answer-Stereoisomerism because of the lack of rotation around the carbon-carbon double bond E-isomer - answer-The same groups are across the double bond Trans isomer Z-isomer - answer-The same groups are on the same side of the double bond Cis isomer Adding hydrogen to C=C bonds produces alkanes - answer-Ethene will react with hydrogen in an electrophilic addition reaction to produce ethane Nickel catalyst 150ºC Halogens react with alkenes to form dihaloalkanes - answer-Electrophilic addition Orange bromine water decolourises when mixed with an alkene and forms a dibromoalkane Alkenes undergo electrophilic addition with hydrogen halides - answer-Two haloalkanes are formed Markownikoff's rule- The major product is the one where hydrogen adds to the carbon with the most hydrogens already attached Addition polymers - answer-Alkenes (monomers) join up and the double bond is removed Alcohols - answer-Primary Secondary Tertiary Halogen + Alcohol ----> - answer-Haloalkane The -OH is substituted by the halide Acid catalyst required such as sulfuric acid Dehydration - answer-Alcohols can be dehydrated to form alkenes Concentrated sulfuric acid or phosphoric acid Heated Oxidising alcohols - answer-Oxidising agent- acidified potassium dichromate (VI) Primary alcohols ----> Aldehydes (distill) and then carboxylic acids (reflux) Secondary alcohols ----> Ketones Tertiary alcohols will only oxidise by being burnt Hydrolysis - answer-Haloalkanes can be hydrolysed to make alcohols in a nucleophilic substitution reaction Warm aqueous alkali solution (Sodium hydroxide) CFCs (Haloalkanes) - answer-Stable, volatile, non-flammable and non-toxic Refluxing - answer-Vertical Liebig condenser Prevents loss of volatile substances Continuously boils,evaporates and condenses the vapours Seperation - answer-Separating funnel with water added to mixture Anhydrous salt (Magnesium sulfate) can be added to remove water after separation