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chemistry 11 > topic test three > Flashcards

topic test three Flashcards

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1
Q

what is energy

A

the capacity to do work or cause change

  • energy change: due to bond breaking / forming
  • stored energy: due to attractive and repulsive forces between particles
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2
Q

what is a system / surroundings

A
  • system: reactant and products

- surroundings: everything surrounding / outside of the system (not included in the reaction)

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3
Q

what is the law of conservation of energy

A
  • states that energy cannot be created or destroyed

- can be transferred / changed from one form to another

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4
Q

What is bond breaking and forming

A

In nearly all reactions intermolecular and intramolecular forces/bonds are broken in the reactants to form new products

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5
Q

What is an exothermic reaction

A
  • reaction that causes temperature of system to rise consequently heat flows out of the system (into surroundings)
  • reacting system loses energy to the surroundings thus enthalpy decreases
  • enthalpy change is negative
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6
Q

What is an endothermic reaction

A
  • reaction that cause temperature of system to fall, consequently heat flows into the system (gains heat from surroundings)
  • reacting system gains energy from surroundings thus enthalpy decreases
  • enthalpy change is positive
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7
Q

what are physical changes

A
  • involve breaking / making of weak bonds
  • require small amounts of energy
  • state changes (melting, boiling, freezing, dissolving, vaporisation)
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8
Q

what are chemical changes

A
  • involves breaking / forming of strong chemical bonds
  • large amount of energy is required
  • when new products are being formed
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9
Q

what is enthalpy

A
  • total energy present in the substance

- different reactions have different enthalpies as strength of bonds varies depending on each substance

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10
Q

what is the amount of enthalpy in a system

A
  • the amount of energy released / absorbed by surroundings
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11
Q

what is change in enthalpy

A
  • /\H is measure in kJ

- /\H = H(products) - H(reactants)

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12
Q

what is the transition state / activated complex

A
  • maximum potential energy (Ep) in the reaction
  • represents stage where bond breaking (endo) and forming (exo) occurs
  • unstable and exists temporarily, once formed changes quickly to products or returns to reactants
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13
Q

what is the activation energy

A
  • Ea: minimum amount of energy required for a successful collision which results in a reaction occurring
  • referred to as Ea barrier which must be overcome for a reaction to occur
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14
Q

how does one measure rate of reaction

A
  • amount of substance use or produced / time taken
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15
Q

what is the collision theory

A
  • collision must occur for a chemical reaction to occur

- minimum specific amount of energy and favourable orientation is required for successful collisions

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16
Q

what are the factors affecting ror

A
  • temperature: ^temp = ^kinetic energy of reacting particles and distribution of molecules (^velocity / movement / successful collisions / sufficient energy to overcome Ea)
  • subdivision: ^SA (makes reactants smaller) = ^exposure to reactants / more collisions in given space (more successful collisions / Ea)
  • nature: gases (more complex bond breaking / forming), solutions (no energy required to break intermolecular bonds)
  • catalyst: provides alternate pathway with lower Ea (^successful collisions / sufficient Ea)
  • concentration: ^c = ^ particles / collisions / Ea
  • pressure: ^p = ^con. of particles (^ collisions / Ea)
17
Q

explain the bonding involved in water

A
  • covalent (intramolecular) bonds between H and O atoms
  • weak dispersion forces (weakest intermolecular force) between water molecules
  • hydrogen bonding (strongest intermolecular force, but still much weaker than covalent) between water molecules
18
Q

what are dispersion forces

A
  • polar: electrostatically attracted to other molecules (one side of the molecule being slightly more positive and the other slightly more negative)
  • non polar: (no overall charge distribution) the molecules still need to be attracted to each other
  • e are always moving: spend more time in one area than another, area becomes temporarily more -ve (other side temporarily more +ve)
  • if non-p comes close to another molecule which has temporary +ve/-ve sides (dipole), temporary attraction occurs, happens throughout substance.
19
Q

MP and BP of water

A
  • MP: 0C
  • BP: 100C, intermolecular forces (force between molecules) are broken, covalent bond holding H and O atoms together are not broken
  • BP: is high compared to other molecular compounds (H bond is strongest intermolecular force)
20
Q

surface tension as a property of water

A
  • very high
  • molecules are held together relatively strongly (H bonding occurring in all directions)
  • surface layer there is no water molecules above to ‘pull up’ these molecules so the surface molecules tend to be pulled back into the liquid
21
Q

density as a property of water

A
  • liquid: cool water is denser than warm water, particles move closer tougher in a smaller amount of space
  • solid: less sense than water, molecules slow right down, for, more H bonds which holds the, in an open hexagonal structure (prevents close packing)
22
Q

what is solubility

A
  • the extent to which a solute will dissolve in a solvent
23
Q

polar and non polar solutes

A
  • P: polar solute dissolves in polar solvent, are hydrophilic (water loving), dissolve in water
  • NP: np solute dissolves in np solvent, are hydrophobic (water hating), don’t dissolve in water
24
Q

what are factors affecting solubility

A
  • amount, nature, temperature, pressure of solvent / solute
  • temp: solids and liquids (^temp = ^solubility), gases (decreased temp = ^ solubility)
  • pressure: little affect on solids and liquids, decreased pressure of gas = decreased solubility
25
Q

what are electrolytes

A
  • a produces ions in a solution
  • ionic substances dissociate (break down) to form ions
  • covalent substances ionise (break down) to form ions
  • strong: completely dissociate and partially ionise
  • weak: partially ionise (double arrow)
  • non: do not dissolve in water
26
Q

what is concentration

A
  • strong solution has more particles than a weak in the same amount of solvent
  • [ppm] = m(solute mg) - m(solution kg)
  • calculations: n=cV, m=cV, n=m/M
27
Q

types of concentrated solutions

A
  • unsaturated: contains less solute than it is able to dissolve at a given temperature
  • saturated: contains as much solute as it can dissolve at a given temp / pressure
  • supersaturated: contains more solute than a saturated solution under existing conditions
    • stable/unstable: when temp changes some compounds release excess solute / some are stable and don’t
28
Q

what is an acid

A
  • pH more than 7
  • sour, turns blue litmus paper red, corrosive, conduct electricity, react with carbonate to form CO2, react with some metals to form H2, react with bases to form water
  • common acids: HCl, H2SO4, H2SO3, CH3COOH, H2CO3, HNO3, NH4CO3, NH4NO3, C6H8O7, CH3CH(OH)COOH
29
Q

what is a strong acid / weak acid

A
  • strong: completely ionise to produce ions in solution
  • e.g. HNO3 (nitric), H2SO4 (sulfuric), HCl (hydrochloric), HBr (hydrobromic), HI (hydroiodic) HClO4 (perchloric)
  • other acids (weak): partially ionise (ethanoic, hydrofluroic, carbonic)
30
Q

what is a base

A
  • pH >7, taste bitter, turns red litmus paper blue, can be corrosive, conduct electricity, feel slippery, do not react with most metals, react with acids to form water
  • common bases: NaOH, NH3, Ca(OH)2, NaHCO3, CaO, Na2CO3
31
Q

what are strong / weak bases

A
  • strong bases: completely dissociate to produce OH ions (group I / II and metal OH)
  • other bases (weak): carbonates, ammonia, other hydroxides are completely dissociated
32
Q

what is Arrhenius’s theory

A
  • states that an acid is a substance that will ionise in solution producing H (aq) ions
  • a base is a substance that will dissociate in solution releasing OH (aq) ions
  • neutralisation: acidic (H) and basic (OH) = neutralisation
33
Q

what are the limitations of Arrhenius’s theory

A
  • some substances behave as bases (produce OH ions in solution) that do not contain OH in their formula (NH3, CO3)
  • only applies to acids / bases in water and not in other solvents
  • some reactions cannot be explained
  • not all salts are neutral, can be basic or acidic
  • H+ ion cannot exist for very long in water
    - H (aq) + H2O (l) –> H3O+ (aq) (hydronium ion): in an aqueous solution, an acid should said to produce H3O + (aq) ions
34
Q

what is the bronsted-Lowry theory

A
  • states that transfer of hydrogen ion (proton) from one reactant to another. acid loses proton (H+) proton donor and base gains proton (H+) proton acceptor
35
Q

what is pH

A
  • measure of concentration of hydrogen ions, a neutral solution has equal concentrations of H and OH ions
36
Q

explain self ionisation in water

A
  • H2O (l) + H2O (l) H3O+ (aq) + OH- (aq)
  • at 25C, c(H3O+) = 1 x 10-7 mol/L, since H3O+:OH- is 1:1, c(OH-) must also be 1 x 10-7 mol/L
  • neutral: c(H3O+) = 1 x 10-7 mol/L, c(OH-) = 1 x 10-7 mol/L
  • acidic: c(H3O+) > 1 x 10-7 mol/L
  • basic: c(OH-) > 1 x 10-7 mol/L or alternatively, c(H3O+)
37
Q

logarithms and pH

A
  • pH = - log [H+], therefore [H+] = 10-pH

chemistry 11 (4 decks)

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