Chemistry PDF

Chemistry **Chap 3** Limiting reactant-reactant that is completely used up.( in order to get the maximum yield of product at minimum cost) Excess amount-Not used up **Chap 4**\ Valence shells and valence electrons -The chemical behaviour of an atom is determined by the electrons\ that are acces...

Chemistry **Chap 3** Limiting reactant-reactant that is completely used up.( in order to get the maximum yield of product at minimum cost) Excess amount-Not used up **Chap 4**\ Valence shells and valence electrons -The chemical behaviour of an atom is determined by the electrons\ that are accessible to an approaching chemical reagent -- Electron Lewis Dot Structure\ - Schematic drawings that show how the atoms in a\ molecule are bonded.\ - Able to differentiate between bonding and nonbonding\ valence electrons in a molecule. **ELECTRONEGATIVITY** -ability of the atom to attract bonding electrons\ - Covalent bond becomes polar covalent bond 2 identical atoms (e.g. O2, H2, Cl2) the bonded electrons are shared equally\ between the two identical atoms.\ ♣ The bond is a non-polar covalent bond.\ ♣ The bond moment is zero.\ ♣ The molecule is non-polar molecule. 2 diff atoms -bonded electron results in different attraction -molecule is polar molecule **Chap 5-periodic table** [Group I (the alkali metals)] -Always form +1 ions.\ -All of their compounds are water soluble\ -Soft, low melting points\ -Highly reactive\ -Melting point decreases down the group [Group II (the alkali earth metals)]\ -Always form +2 ions.\ -Relatively soft, relatively low melting points\ -Highly reactive but less so than group I elements [Group VII (the halogens)]\ -Sometimes called group 17\ -Melting point increases down the group\ -Usually form -1 ions\ -Compounds are water soluble except with Ag, Hg and Pb\ -More reactive halogens displace less reactive ones in solution [Group VIII (the noble gases)\ ]-Form almost no compounds (XeF4 is one exception)\ -Have full electronic outer shells\ -Exist as monatomic gases [The Transition Metals]\ -Sometimes called the d-block\ -High melting points\ -Hard\ -Have multiple oxidation states which are frequently coloured.\ -Often used in catalysis [Lanthanides and Actinides]\ -Also called f-block\ -Mostly artificial\ -Uranium is heaviest element naturally found on earth **Chap 6-thermochemistry** [EXOTHERMIC Endothermic]\ Heat is given out to the -heat is absorbed from the surrounding\ surroundings -tmp falls (eg.evaporation ) surrounding temperature rises\ E.g. -dissolve of some ionic compound in\ Combustion of fuels h20\ Dissolving of acids\ Condensation\ Freezing The amount of energy involved in a reaction is known as the heat\ change or **enthalp**y change of the reaction. (ΔH = total energy of products -- total energy of reactants) A diagram of a reaction Description automatically generated  When a chemical reaction occurs, bonds of the reactants are broken\ and new bonds are made to form products. Energy profile diagrams are used to show the enthalpy change and\ activation energy of a reaction.\ Activation energy acts as an energy barrier that must be overcome by\ the reactants before they can react to form products **Chap 7 -chemical reaction** [Effective collision] in order for a reaction to occur,\ ◦ The reactant particles must collide with each other; and\ ◦ They must collide with energy that is equal to or greater than the activation\ energy.\ -When the collisions between reactant particles fulfil these conditions,\ product particles are formed. ◊ Effective collisions.\ -The frequency of effective collisions between particles affects the speed\ of a reaction. -The conc of reactant,pressure,particle size,tmp,presence of catalyst When the concentration of a reactant is increased, the speed of\ reaction increases. More reactant particles\ available to collide with\ each other\ Collisions between\ reactant particles become\ more frequent\ Frequency of effective\ collisions increases\ Higher speed of reaction\ Increase in\ concentration -At higher pressure,particles of gaseous reactants are closer tgt hence higher speed. -total surface area is increased. When temperature is increased, the reactant particles gain energy,\ move faster and collide with each other more often. ◦ At higher temperatures, more particles possess energy equal to or\ greater than the activation energy, resulting in a higher frequency of\ effective collisions. **Catalyst** A catalyst is a substance which increases the speed of a chemical\ reaction and remains chemically unchanged at the end of the\ reaction.(eg.iron,platinum) Catalysts increase the speed of\ reaction by providing an\ alternative pathway for the\ reaction to proceed For the catalyzed reaction, where the activation energy is\ lower,\ ◦ More colliding particles possess energy equal to or\ greater than the activation energy\ ◦ The frequency of effective collisions increases, resulting in\ a higher rate of formation of product particles.\ Thus, the speed of the catalyzed reaction is higher. **Enzymes,** They are biological catalysts.\ Characteristics of enzymes:\ 1. They are proteins\ 2. They are specific in their actions\ 3. They are sensitive to temperature\ changes\ 4. They are sensitive to pH changes Chap 7( II) A white background with black text and black text Description automatically generated An oxidizing agent is a substance that causes another substance to be\ oxidized.\ An oxidizing agent is reduced in the process.\ A reducing agent is a substance that causes another substance to be\ reduced.\ A reducing agent is oxidized in the process