mod 3 Flashcards
what is the formula for decomposition reaction?
chemical A –> chemical B + chemical C
what is decomposition reaction?
one substance changes into two (or more) chemical subtances
what can a decomposition reaction be caused by?
- heat (thermolysis)
- electricity (electrolysis)
- light (photolysis)
what is a combustion reaction?
a chemical substance (fuel) reacts rapidly with oxygen to release energy
what is the formula for combustion reaction?
fuel + oxygen –> carbon dioxide + water
what is needed to start combustion?
- a spark
what is a synthesis reaction?
two (or more) chemical substances react to make one (main, complex) substance
what is the formula for a synthesis reaction?
chemical A + chemical B –> chemical C
what is a precipitation reaction?
two soluble ionic compounds in solution are combined and react to produce a new ionic compound that is insoluble
what happens to the insoluble compound after a precipitation reaction?
the insoluble compound makes the mixture cloudy and eventually ‘falls’ to the bottom which is called the precipitate
what is the formula for a precipitation reaction?
AB(aq) + CD(aq) –> AD(s) + CB(aq)
what are the solubility rules?
- ammonium
- group 1 metals
- nitrate
- acetate
- chlorine, bromine, iodine
- sulfate
what are exceptions to the solubility rules?
- group 1 metals: Li3PO4 (lithium phosphate) is insoluble
- acetate: Fe(CH3COO)3 is slightly soluble and AgCh3COO is slightly soluble
- chlorine, bromine, iodine: AgCl, AgBr, AgI and PbI2 are insoluble and PbCl2, PbBr2 are slightly soluble
- sulfate: BaSO4, PbSO4 are insolube & CaSo4, Ag2SO4 are slightly soluble
what are the insolubility rules?
- hydroxide
- carbonate
- phosphate
what are exceptions to the insolubility rules?
- hydroxide: group 1 salts, ammonium & Ba2+ / Ca(OH)2 and Sr(OH)2 are partially soluble
- all carbonates, phosphates and sulfide: group 1 and ammonium
what is complete combustion?
occurs when there’s excess oxygen present
what is incomplete combustion?
occurs when there’s and insufficient supply of oxygen
what is the formula for acid and reactive metals reactions?
acid + reactive metal –> salt + hydrogen
what is the formula for acid and base (neutralisation) reactions?
acid + base –> salt + water
what is the formula for acid and carbonate reactions?
acid + carbonate –> salt + carbon dioxide + water
how do Aboriginals and Torres Strait Islander people remove toxins from their food?
- three ways to remove cycasin toxin
- brief leaching
- prolonged leaching
- aging & fermentation
what is brief leaching?
cooked to denature toxin (less harmful) –> crushed to increase surface area –> leached overnight = placed in bags in a running stream (soluble toxin removed) –> eaten
what is prolonged leaching?
crushed to increase surface area –> leached over 3-9 = placed in bags in a running stream (soluble toxin removed) –> cooked to denature toxin –> eaten
what is aging and fermentation?
seeds buried under cycad plant in moist soil –> anaerobic micro-organisms act on seeds over weeks –> fermentation produces alcohol dissolves toxin into soil –> removed –> eaten
what is metal displacement?
when one metal takes the place of another metal in that metal compounds solution
what do metal displacements show?
they show that the first metal is more reactive than the second metal
why are more reactive metals on the left of the periodic table?
- have lowest no. of protons
- valence electrons lost easily
- lower ionisation energy
why are more reactive metals lower on the periodic table?
- atoms have a larger atomic radius
- valence electrons have small charge
- valence electrons lost easily
- lower ionisation energy
what is a redox reaction?
invloves an oxidation half-step and a reduction half-step
what is oxidation?
oxidation is the first step and occurs when a chemical loses one or more electrons
what is reduction?
reduction is the second step and occurs when a chemical gains one or more electrons
what is an oxidation half-equation?
X –> X+ + e-
what is an reduction half-equation?
Y2+ + 2e- –> Y
what is an oxidant?
an oxidising agent that causes oxidation to occur by being reduced itself
what is a reductant?
a reducing agent that causes reduction to occur by being oxidised itself
what are oxidation numbers?
they are assigned to chemical species in a reaction to help us identify which has undergone oxidation and reduction
what happens if the oxidation numbers increase?
oxidation has occured
what happens if the oxidation numbers decrease?
reduction has occured
what are the rules for assigning oxidation numbers?
- zero for an element in its pure state
- same as charge for a monatomic ion, whether it’s free or in an ionic compound
- for hydrogen it’s +1 when it’s bound to non-metals, when by itself it’s 0
- for oxygen, it’s -2 in all cases when it’s in a compound, when by itself it’s 0
- sum of oxidation number must:
a) equal zero for a neutral compound
b) equal charge of polyatomic ion
what is a galvanic cell?
a galvanic cell or electrochemical cell is made up of two half-cells that are connected so that chemical potential energy is converted to electrical energy (rather than heat)
how do you set a up a galvanic cell experiment?
- each half-cell consists of an element in its ionic solution
- a wire connects metal electrode that are dipped in the solutions
- a salt bridge connects the solutions to complete the circuit
what can galvanic cells be used to show?
shows the reactivity of metals compared under controlled conditions
what are controlled variables in a galvanic cell experiment?
- temperature 25°C
- pressure 100kPa
- concentration 1.000M
what do you use standard potentials for?
- to predict the activity series of metals
- to predict the reaction of metals in solutions
- to calculate the voltage of a given Galvanic cell
- to calculate the voltage for any redox reaction
how do you predict the activity series of metals?
- read the oxidation half-equation for metals
- the higher the E° value, the more reactive the metal
how do you predict the reaction of metals in solutions?
- list all the chemical species in the beaker, including water
- find the most likely oxidation half-step by reading DOWN from top to right
- find the most likely reduction half-step by reading UP from the bottom left
- calculate the E° value to see if it’s +ve
- all negative E° value shows a reaction that will not occur spontaneously
what is collision theory?
chemical reactions that can be seen as the effective collision of reactant particles, together so that new substances are formed
what is required for an effective collsion?
- reactant particles
- to collide with sufficient energy
- to collide with correct orientation
what is an energy profile diagram?
shows the energy in the reactants and products during a chemical reaction as well as in the imagined transition state between them
what is the rate of reaction?
the rate of a chemical reaction refers to how fast (or slow) a chemical reaction occurs
how can a chemical reaction be measured for solutions?
we can use the change in concentration per second
how can a chemical reaction be measured for gases?
can use volume of gases formed per second OR the mass loss per second
what are the 5 factors that can change the rate of reaction?
- increasing temperature increases the rate of reaction
- increasing the surface area of solid reactants
- increasing concentration of solutions that are reactants
- increasing the pressure of gases reactants
- using catalysts
how does increasing the temperature increase the rate of reaction?
- increases the average kinetic energy of reactants so that more collisions occur, and they occur with more sufficient energy
how does increasing the surface area of solid reactants increase the rate of reaction?
- increases the likelihood of collisions
- increasing the surface area can be achieved by grinding the reactant into smaller pieces
how does increasing the concentration of solutions that are reactants increase the rate of reaction?
- increases the number of reactants in a certain volume, thus increasing the likelihood of collisions
how does increasing the pressure of gases reactants increase the rate of reaction?
- increase the number of reactants in a certain volume, thus increasing the likelihood of collisions
- increasing the pressure can be achieved by adding more reactant gas into the same volume or decreasing the volume of the reaction chamber
how does using a catalyst increase the rate of reaction?
- a catalyst is any substance that increases the rate of a chemical reaction. without being changed permanently in the reaction
- it works by reducing the activation energy
- lowering activation energy mean that less energy is required to get chemicals to react
what are different types of catalysts?
- homogenous
- heterogenous
what is a homogenous catalyst?
is in the same physical state as reactants and products
what is a heterogenous catalyst?
catalyst that’s in a different physical state to reactants and products
what is calorimetry?
is the technique of measuring the heat released or absorbed by a chemical process
