Developing fuels Flashcards
What is the molar volume of a gas at room temperature and pressure?
The molar volume is about 24.0 dm³ at 298 K (25 °C) and 100 kPa.
What is the ideal gas equation?
pV = nRT, where p is pressure (Pa), V is volume (m³), n is moles, R is the gas constant (8.314 J mol⁻¹ K⁻¹), and T is temperature (K).
How is gas volume measured?
Using a gas syringe or an inverted burette/measuring cylinder in water.
What is a σ bond?
A σ bond is formed by the direct overlap of orbitals in a straight line, creating an area of increased electron density.
What is a π bond?
A π bond is formed by the sideways overlap of p orbitals, creating areas of electron density above and below the σ bond.
Which bond is stronger, σ or π?
A σ bond is stronger than a π bond.
How are 3-D molecular diagrams represented?
Bonds in the plane of the paper are straight lines, bonds behind are dashed wedges, and bonds in front are solid wedges.
What is enthalpy?
Enthalpy is the energy change in a chemical reaction, calculated as the difference between energy absorbed breaking bonds and energy released making bonds.
What is an exothermic reaction?
An exothermic reaction releases energy, causing a negative enthalpy change (ΔH).
What is an endothermic reaction?
An endothermic reaction absorbs energy, causing a positive enthalpy change (ΔH).
What are standard conditions for enthalpy changes?
298 K, 1 atmosphere (101 kPa) pressure, and 1 mol dm⁻³ concentration for solutions.
What is the standard enthalpy change of reaction (ΔrH°)?
The enthalpy change when molar quantities of reactants react under standard conditions.
What is the standard enthalpy change of combustion (ΔcH°)?
The enthalpy change when one mole of a substance is completely burned in oxygen under standard conditions.
What is bond enthalpy?
The average energy required to break one mole of a specific bond in the gaseous state.
How do bond enthalpies relate to bond lengths?
Bonds with higher enthalpies typically have shorter bond lengths.
What is the formula for energy transferred when heating water?
q = mcΔT, where m is mass (g), c is specific heat capacity (4.18 J g⁻¹ K⁻¹), and ΔT is temperature change (K).
What is Hess’s law?
The enthalpy change of a reaction is independent of the path taken, provided the initial and final conditions are the same.
What is a catalyst?
A substance that speeds up a reaction by providing an alternate pathway with lower activation energy, without being chemically changed.
What is cracking?
Cracking is breaking large hydrocarbons into smaller ones, often requiring high temperatures and pressures or a catalyst.
What are common atmospheric pollutants from combustion?
Particulates, CO, CO₂, NOₓ, and SOₓ.
What is benzene?
Benzene is an aromatic hydrocarbon (C₆H₆) with delocalised π electrons over a ring structure.
What is a saturated hydrocarbon?
A hydrocarbon containing only single C-C bonds, such as alkanes.
What is the general formula for alkanes?
CₙH₂ₙ₊₂.
What is an addition reaction?
A reaction where a molecule adds to a double bond, forming a single product.
What is electrophilic addition?
An addition reaction where an electrophile accepts a pair of electrons from a double bond.
How can bromine water test for unsaturation?
Unsaturated compounds decolourise bromine water as they form dibromo compounds.
What is the general equation for complete combustion?
Fuel(l/g) + O₂(g) → CO₂(g) + H₂O(g).
What is addition polymerisation?
A process where monomers with double bonds form long-chain polymers by breaking their double bonds.
What are structural isomers?
Compounds with the same molecular formula but different arrangements of atoms.
What are E/Z isomers?
Isomers with restricted rotation around a double bond, where E has groups on opposite sides and Z has groups on the same side.
What are biofuels?
Fuels made from plant or animal materials, which can be carbon-neutral if plants reabsorb CO₂ during growth.
What are the conditions required for cracking?
High temperatures and pressures or the use of a catalyst.
What is the general formula for cycloalkanes?
CₙH₂ₙ.
What is the test for unsaturation?
Shake the sample with bromine water; if the solution decolourises, the compound is unsaturated.
What is the formula for calculating energy transferred when heating a solution?
q = mcΔT, where q is energy (J), m is mass (g), c is specific heat capacity (J g⁻¹ K⁻¹), and ΔT is temperature change (K).
What are the units for bond enthalpy?
kJ mol⁻¹.
What is the enthalpy change of neutralisation?
The enthalpy change when one mole of H⁺ reacts with one mole of OH⁻ to form one mole of water under standard conditions.
What is photochemical smog?
A type of air pollution formed when sunlight reacts with pollutants like nitrogen oxides and hydrocarbons, producing harmful compounds such as ozone.
What is the functional group of carboxylic acids?
-COOH (carboxyl group).
What is the general formula for alkenes?
CₙH₂ₙ.
What are the by-products of combustion of sulfur-containing fuels?
Sulfur dioxide (SO₂), which contributes to acid rain.
What is the role of ammonia in reducing NOₓ emissions?
Ammonia reacts with NOₓ to form nitrogen and water, reducing emissions.
What is a repeating unit in a polymer?
The smallest structure in a polymer chain that repeats to form the entire polymer.
What is hydrogenation of alkenes?
The addition of hydrogen to an alkene, converting it into an alkane, using a catalyst.
What is the functional group of alkenes?
A C=C double bond.
