obtaining energy from fuels AOS1

Question 1

how to calculate the mole ratio?

Answer 1

the mole or coefficient of the unknown chemical/the mole or coefficient of the known chemical

Question 2

how to do gas volume-volume calculations?

Answer 2

when all species in a chemical eq are in the gaseous state, and the temp + pressure are constant, the mole ratio will also be a volume ratio

Question 3

what’s the quantity of energy released in a reaction?

Answer 3

the quantity of energy released when a fuel undergoes combustion is directly proportional to the amount of fuel used

Question 4

what’s complete vs. incomplete combustion?

Answer 4

complete combustion produces CO2 and H20 as products and occurs when sufficient oxygen is available or it’s in excess + releases more energy whilst incomplete combustion forms carbon monoxide and sometimes carbon and occurs when the oxygen supply is limited

Question 5

what’s a greenhouse gas?

Answer 5

all carbon-based fuels undergo combustion to produce the greenhouse gases CO2 and H20. but this gas is a gas that can absorb infrared radiation and. its increasing around the world which contributes to global warming

Question 6

what are some examples of greenhouse gases?

Answer 6

CO2, H20 and CH4 (methane used as a fuel for both natural gas and biogas)

Question 7

what’s a reagent?

Answer 7

a substance added to a system to cause a chemical reaction

Question 8

what does it mean if a chemical is in excess?

Answer 8

some of the other reactants will remain unreacted and be left over once the reaction has ceased (not completely consumed)

Question 9

what’s a limiting reactant?

Answer 9

the reactant that’s completely consumed in the reaction, the amount of the limiting reactant must always be used to determine the amount of product that will be formed

Question 10

how to calculate the limiting reactant?

Answer 10

calculate the no. of moles of each reactant, identify which reactant is the limiting one and use the amount of limiting reactant to determine the amount of product formed

Question 11

how to calculate the amount of excess reactant left over?

Answer 11

subtract the number of moles reactant of a certain chemical from the initial to find this

Question 12

what’s specific heat capacity?

Answer 12

of a substance is a measure of the amount of energy (J) needed to increase the temp of a specific quantity of that substance usually 1g by 1C, reflects the type of bonding in a substance (water, hydrogen bonding)

Question 13

how to calculate the energy content of a food or fuel?

Answer 13

energy content=q/m, m is change in m though during combustion, and q is the energy transferred to the H20

Question 14

how to avoid heat loss?

Answer 14

putting a lid on a container, insulating the beaker of water/solution with flameproof material and placing insulation around the burning fuel and heat loss represents a systematic error

Question 15

what’s a bomb calorimeter?

Answer 15

a piece of equipment used for measuring the energy released by combustion reactions that involve gaseous reactants or products and is designed to withstand high pressures and the energy content of fuels is measured by burning them in a bomb calorimeter, to is a sealed oxygen-filled vessel which is surrounded by a KNOWN volume of water

Question 16

what’s solution calorimetery?

Answer 16

it measures energy changes for reactions that occur in a solution, could be as simple as a polystyrene foam coffee cup with a lid but this isn’t great because it absorbs some heat so the temp change is lower than it should be

Question 17

what’s calorimetry?

Answer 17

the experimental method of measuring the heat energy released/absorbed by a chemical reaction of physical process like by the combustion of a fuel

Question 18

what does calorimetry show?

Answer 18

if the temp of the water decreases then it’s an endothermic reaction whilst if it increases then the reaction occurring in it is exothermic

Question 19

what does calibration involve?

Answer 19

adding a known quantity of that energy from an electrical source or from a chemical source

Question 20

what happens during electrical calibration?

Answer 20

the value of the temp change may be affected by heat loss from the calorimeter so a temp-time graph may be used to determine a more accurate value of the change in T

Question 21

how to calculate energy efficiency?

Answer 21

useful energy/energy input x 100

Question 22

what’s the energy efficiency of a coal-fired power station?

Answer 22

approx 30%