Periodic Table And Energy Flashcards

Question

Why ammonia is added after halide test?

Answer 1

To confirm results when the colours could be ambiguous Reaction that occurs: AgX(s) + 2NH3 (aq) —> [Aq(NH3)2] (s) + X- (aq) Where’s X is Br or Cl not I

Answer 2

Cl2 + H2O —> HClO + HCl HClO dissolves to form ClO- (chlorate (1) Ions) & HClO (hypochlorocic acid)- bleach This is a **disproportion rections** as the chlorine is both oxidised from ON =0 (Cl2) to ON= +1 (HClO) as well as reduced to ON= -1 (HCl) in the same step

Answer 3

Cl2 + 2 NaOH —> NaClO + NaCl + H2O This is **disproportion rections** as the chlorine is both oxidised from ON =0 (Cl2) to ON= +1 (NaClO) as well as reduced to ON= -1 (NaCl) in the same step

Answer 4

Mg(OH)2 is slightly soluble & lower dissociation so pH 10 Ba(OH)2 is much more soluble & higher dissociation so pH 13 Down group 2: - solubility increases -pH increases - Alkalinity increases

Answer 5

Ca(OH)2 added to fields to increase pH of acidic soils as it neutralises acid in soil forming neutral water Ca(OH)2 [s] **+** 2H+ [aq] **—>** Ca+ [aq] **+** 2H2O [l]

Answer 6

Often uses at antacids for treating indigestion E.g magnesium hydroxides/carbonate Mg(OH)2 [s] **+** 2HCl [aq] **—>** MgCl2 [aq] **+** 2H2O [l] Or Calcium carbonate CaCO3[s] **+** 2HCl [aq] **—>** CaCl [aq] **+** 2H2O [l] **+** CO2 [g]

Answer 7

1) test for Carbonates - using dilute nitric acid ( HNO3) 2) test for sulfates - using barium nitrate 3) test for halogens - using silver nitrate then ammonia

Answer 8

1) add sodium hydroxide to from ammonia +water 2) release ammonia gas by heating gently 3) test for ammonia using damp litmus paper -> blue if positive NH4+ [aq] **+** OH- [aq] **—>** NH3 [g] **+** H2O [l]

Answer 9

1) the rate is fastest at start of reaction due to highest concentration of reactants -steepest curve 2) rate of reaction slows down as reaction proceeds as reactants are being used up. - shallowing out 3) once reactants have been used to rate of reaction is zero - graph plateaus

Answer 10

**adv** - speed up rate of reaction which saves money because plant doesn’t have to be open as long - allow reactions to occur at lower temperature reducing carbon footprint - save industries money by reducing fuel cost - can be used repeatedly **disadv** - very expensive to buy - need to be removed from products before reused - different reactions use different catalysts - catalysts can be ruined by impurities - heavy metal extractions create toxic contamination

Answer 11

**Heterogeneous** = catalyst in different phase from the reactant the reaction occurs on its surface. Reactant binds (absorbs) to the surface increasing likelihood of meeting and inducing stress in bonds lower AE **homogeneous** = catalyst and reactant are in same phase, the reaction proceeds through an intermediate species. The catalyst is changed into a product and then that product is used and reforms the catalyst. These 2 reactions require less energy overall.

Answer 12

Boltzmann distribution shows the number of molecules with a given energy. Knowing activation energy in relation to energy of particles allows you to find area under curve which= particles above Ea that will react if collide.

Answer 13

Temperature increase 1) peak moves to the right 2) peak broadens 3) peak lowers Overall result more particles with Ea so rate of reaction increases as more successful collisions

Answer 14

See notes Exothermic - goes down in level as heat is given out Endothermic- goes up in level as energy is taken in from surroundings

Answer 15

The minimum energy requires for a reaction to take place

Answer 16

The physical states under standard conditions of a chemical E.g solid/ liquid/ gas at RTP

Answer 17

The heat energy change that occurs during a process under constant pressure

Answer 18

Enthap change asociated with a stated equation

Answer 19

Enthalpy change when 1 Mol of a compound is fromed from its elements in their standard states

Answer 20

Enthalpy change when 1 mole of a substance undergoes complete combustion

Answer 21

Enthalpy change when 1 mole of water is formed from 1 mole of aq H+ nad 1 mole of OH-

Answer 22

Pressure of 100 KPa and temperature of 298 K Plimsoll line (⦵ ) used to indicate standard conditions (it appears after the H)

Answer 23

(Sum of bonds broken) - (sum of bonds formed) = enthalpy change If negative reaction = exothermic If positive reaction = endothermic (This however is an average value)

Answer 24

**calorimetry** 1) coffee cup calorimeter - insulated polystyrene cup with measured volume of water with which reaction occurs - temp change of water is measured using SHC of water energy change is calculated - insulation is used around polystyrene cup to minimise heat loss to surroundings 2) Copper cup Calorimeter - copper cup with known volume of water is heated above fuel - same as above to calculate energy change - fraught shields used to minimise heat loss to surroundings

Answer 25

**Q = mc ∆T** Where: Q - energy change in J M- mass of water/ solution in g C- specific heat capacity of water (solution assumed pure water) = 4.18 Jg-1oC-1 ∆T - change in temperature of water in oC

Answer 26

**∆H = -q/ n** Negative energy change used (-q) - as energy the chemicals lost is what was gained bu the surrounding we measured +if you have 2 values for moles use the lowest one s this reaction is what is limiting in the reaction

Answer 27

1) if you draw a cooling curve graph - draw a vertical line from the time that solutions were mixed (beginning of reaction) - draw straight diagonal line from the downwards path of graph Were those two points meet is the max temperature reached ∆T which can the be used in calculations **[ see notes for more info]** 2) if you calculate from a known reaction then you can find mc =C that can be used with you later reactions See notes

Answer 28

Draw out cycle Use arrows as vectors Formation = compound formed from elements in their standard states

Answer 29

Phosphorus has more electrons in its bonded molecule therefore stronger/more London forces that require more energy to break than Cl2

Answer 30

Electrical conductivity High melting and boiling points Don’t dissolve (low solubility)

Answer 31

High melting points Insoluble Non conductive

Answer 32

Across period 2 & 3 - melting point increases from group 1 to group 4 - sharp decrease in melting point between group 4 and group 5 Due to change from giant to simple molecular structures - melting point comparatively low from group 5 to group 18 Giant structures have strong forces to becomes so high melting point whereas simple molecular have weaker intermolecular forces

Answer 33

Breaking 1 mol of bonds in gaseous molecules

Answer 34

Group 2 oxide react with water —. Releasing OH ions forming alkaline solution CaO(s) + H2O —> Ca2+ + 2OH-(aq) Group 2 are weakly alkaline with elements further down having increased alkalinity

Answer 35

At RTP all halogens exists as diatomic molecules (X2) Down group 7 - more electrons - stronger London forces - more energy to break London forces - boiling point … increases down group

Answer 36

Q (energy) = m (mass of water/solvent) c (specific heat capacity) T (change in temp) Enthalpy change = -Q/moles

Answer 37

In a close system when the rate of the forward reaction is equal to the rate of the reverse reaction and the concentrations of the reactants and products do not change