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DIY chem > Mod 3 > Flashcards

Mod 3 Flashcards

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1
Q

What is first ionisation energy

A

. Energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions
. In equation always include state symbols and correct charges

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2
Q

What exceptions are there in first ionisation energy

A

. Between groups 2 to 3 there is a decrease
. MGs outer electron in three a sub shell and Al in 3p sub shell 3p has higher energy level so slight increase in shielding
. Between group 5 to 6 there is a decrease
. Shielding identical and electron being removed from 3p sub shell so sulfur is easier to remove

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3
Q

What is second ionisation energy

A

. The energy needed to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

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4
Q

What are the trends in successive ionisation energies

A

. Increase is more electrons are removed
. Electrons are removed from a more positive ion
. Attraction between remaining electrons and nucleus increases radius also decreases
. more energy needed to remove the next electron

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5
Q

Explain the trend in reactivity in group 2 metals

A

. Reactivity increases down the group as shielding increases atomic radius increases nuclear charge increases but is outweighed by increasing atomic radius and shielding so nuclear attraction of outer electron decreases so less energy required to remove electrons

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6
Q

Explain group 2 metals solubility with sulphate and hydroxide

A

. Sulphate solubility increases up the group
. Hydroxide solubility increases down the group

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7
Q

What use does CA(OH)2 have

A

. Using agriculture to neutralise acidic soils

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8
Q

What are use does MG(OH)2 and CACO3 have

A

. Used an indigestion tablets antacids to neutralise excess stomach acid

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9
Q

What are used to BaSO4 has

A

. Barium meals because BASO4 is insoluble

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10
Q

What is periodicity

A

. Repeating pattern in chemical and physical properties

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11
Q

What is the trend in atomic radius across a period and across a group

A

. Decreases across period as number of protons increases so I was for electrons in the same shell have similar shielding so strong nuclear attraction makes electrons be drawn in more
. Increases down the group as number of shells increases

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12
Q

Describe Melting and boiling points down Group 8

A

. Number of electrons in atomic radius increases the strength of induced dipole dipole interactions increases which requires more energy to overcome

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13
Q

Explain the trending reactivity in halogens

A

. Less reactive down the group as atomic radius increases so outer electrons further from nucleus and more shielded so less nuclear attraction so more difficult to attract electrons

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14
Q

Explain displacement reactions in halogens

A

. More reactive halogens will oxidise halide ions of less reactive halogens

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15
Q

What colour do chlorine bromine and iodine go in aqueous halogens And when dissolved in organic solvent

A

. In aqeous halogens pale green, orange, brown
. Inorganic solvent pale green, orange, violet

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16
Q

How do you test for halide ions

A

. Dissolve unknown halide in water with nitric acid
. Aqueous solution of silver nitrate added
. Silver ions from the silver nitrate react with halide to form silver halide precipitate
. If colour change not obvious enough add ammonia solution

. Ag+ + Cl- —> Agcl, soluble in dilute nh3, white
. Ag+ + Br- —> Agbr, soluble in conc nh3, cream
. Ag+ + I- —> AgI, insol in nh3, yellow

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17
Q

What is disproportionation

A

. Simultaneous oxidation and reduction of the same element

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18
Q

What is the equation to make bleach and what are its uses

A

. CL2 + 2NAOH —> naCl + NaClo+ H2O
. Ionic Cl2 + 2OH- —> Cl- + ClO- + H2O
. Water treatment, bleaching paper and textiles, cleaning toilets

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19
Q

What reaction takes place between chlorine in water

A

. Cl2 + H2O —> HCl+ HCLO

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20
Q

What are the advantages and disadvantages of treating water with chlorine

A

. S chlorine added to drinking water to kill bacteria, prevents growth of algae and prevents discolouration caused by organic compounds
. W. Chlorine is toxic, Clarington react with organic matter to form carcinogenic chlorinated hydrocarbons, liquid chlorine causes chemical burns and eyes and skin

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21
Q

What are the ethical concerns of chlorine in water treatment

A

. Risks from untreated water outweigh risk to cancer
. It’s a form of mass medication

22
Q

What alternatives are there to chlorine in water treatment

A

. Ozone is a strong oxidising agent which kills microorganisms, is expensive and has short half life so not permanent
. Ultra violet kills microorganisms by damaging DNA, ineffective in cloudy water and is only short-term

23
Q

How do you test for different ions

A

. Carbonate-dilute HNO3, fizzing CO32- + 2H+ —> CO2 + H2O
. Sulphate-BA (NO3)2, Insoluble white precipitate Ba2+ + SO42- —> BaSO4
. Ammonia-heat/NAOH, NH3 litmus turns blue NH4+ + OH- —> NH3 + H2O

24
Q

What order should Ion tests be carried out in and why

A

. Carbonate, sulphate, halide
. This prevents false positives

25
Q

What is standard enthalpy change of reaction

A

. Enthalpy change when reaction occurs in molar quantities shown in chemical equation with all reactants and products and their standard states, under standard conditions

26
Q

What is standard enthalpy change of neutralisation

A

. Enthalpy change when solutions of an acid and an alkali react together to form one mole of water, under standard conditions
. -🔺H

27
Q

What is standard enthalpy change of combustion

A

. Enthalpy change when one mole of a substance is completely burned in oxygen, under standard conditions
. -🔺H

28
Q

What is standard enthalpy change of formation

A

. Enthalpy change when one mole of a compound is formed from this elements in the standard state, under standard conditions
. Normally -🔺H

29
Q

What is activation energy

A

. Minimum amount of energy needed for a reaction to start

30
Q

Explain the enthalpy profile diagram for an endothermic reaction

A

. _-
. Reaction absorbs energy
. +🔺H

31
Q

Explain the enthalpy profile diagram for an exothermic reaction

A

. -_
. Reaction that releases energy
. -🔺H

32
Q

What experiment could you use to calculate enthalpy change

A

. Use polystyrene cup, record temperature change of solution, some heat lost as apparatus and surroundings are heated

33
Q

What experiment could you use to calculate enthalpy change for combustion reactions

A

. Use copper calorimeter record temperature change of water during a reaction
. Couldn’t use polystyrene cup because would burn and too much heat lost to surroundings

34
Q

What are the reasons that standard enthalpy change of combustion could be less than the calculator theoretical values

A

. Heat released to the surroundings
. Incomplete combustion or incomplete reaction
. Non-standard conditions

35
Q

What does it mean if a reaction is endothermic or exothermic

A

. If endothermic, more energy required for breaking bonds then released by forming bonds
. If Exothermic more energy released by forming bonds the energy required when breaking bonds

36
Q

What is Hesses law

A

. Total enthalpy change of a reaction is always the same no matter which route is taken

37
Q

What is required for a reaction to take place between two particles

A

. They collide in the correct orientation
. They collide with at least a certain minimum amount of kinetic energy

38
Q

What three factors affect the rate of reaction

A

. Concentration (or pressure for gasses)
. Temperature
. Catalyst

39
Q

What is the effect of concentration/pressure on rate of reaction

A

. Increasing pressure/concentration increases rate of reaction
. There are more particles per unit volume
. There are more frequent collisions

40
Q

What is the effect of temperature on rate of reaction

A

. Higher temperature more molecules have energy above EA
.  more successful collisions

41
Q

What is the effect of a catalyst on the rate of reaction

A

. Provides lower activation energy
. More molecules of energy above activation energy
. So more successful collisions

42
Q

What are the different types of catalysts

A

. Heterogenous catalyst - different phase from reactants
. Homogenous catalyst - same phase as reactants

43
Q

What are the benefits of using catalysts in industry

A

. Reactions carried out at lower temperatures and pressures
. Leads to less fuel is burned and lower CO2 emissions
. Different reactions can be used with greater atom economy and less waste
.  can reduce the use of toxic substances

44
Q

How can you measure the rate of reaction

A

. Change in mass overtime
. Changing gas volume overtime
. Changing concentration

45
Q

How does concentration change as a reaction is carried out

A

. Concentration of reactants greatest at the start of reaction
. Greater number of collisions per second so more successful collisions at start
. Concentration of a reactant decreases as a reaction proceeds
. Rate of reaction decreases as collisions become less frequent with sufficient EA taking place per second
. Concentration of product increases as reaction proceeds and rate decreases

46
Q

What are the features of an equilibrium

A

. Reaction takes place in a close system
. Rate of forward reaction is equal to the rate of reverse reaction
. Concentrations of reactants and products remain constant and do not change

47
Q

What is Le Chatelier’s principle

A

. Position of a dynamic equilibrium shift to minimise the effect of any change

48
Q

What is the effect of changing concentration Of a reactant on equilibrium

A

. Causes equilibrium to shift towards products to counteract the change of concentration

49
Q

What is the effect of changing pressure on equilibria

A

. Increasing pressure causes equilibrium to shift in the direction with less moles to decrease the total pressure to minimise the change in pressure

50
Q

What is the effect of changing temperature on equilibrium

A

. Increasing temperature causes equilibrium to shift in the endothermic direction to minimise the change in temperature

51
Q

What is the effect of catalyst on equilibrium

A

. Catalyst has no effect on position of equilibria, increases the rate of the forward and reverse reactions equally, only increases rate at which equilibriums is established

52
Q

What is KC

A

. Kc=products/reactants
. Is a measure of the position of equilibrium
. If the number is large equilibrium lies to the right (Products are large)
. If the number is small equilibrium lies to the left (reactants are large)

DIY chem (5 decks)

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