MCQs- mistakes Flashcards
what are the features of a system in dynamic equilibrium?
-CONC. OF PRODUCT AND REACTANT NO LONGER CHANGES but they are NOT equal
-equilibrium achieved by both sides
-rate of forward and reverse reaction is equal
-closed system
what are the reasons for why enthalpy change of combustion is less exothermic than textbook values?
-non-standard conditions
-incomplete combustion
-heat loss to surrondings
why was enthalpy change of combustion more exothermic
in the calculations, the student used the molar mass of ethanol instead of methanol
(higher mr-> smaller mol. -> Q/n= greater)
what are the calculations to think about when asked about enthalpy change of combustion
- Q=mcT
- H= Q/n (mol of alcohol burned)
whats the oxidation number of H in non-metals and metals
non-metal= +1
metal= -1
oxidation no. of oxygen including exceptions
normally= -2
in H2O2 aka peroxide= -1
bound to F (OF2) = +2
oxidation no. of chlorine including exceptions
normally= -1
exceptions:
bound to O or F= +1
what occurs at each electrode in a chemical cell
-ve electrode= oxidation (more reactive metal is the electrode)
+ve electrode= reduction (less reactive metal gains electrons)
is 2nd electron affinity exo or endo
endo- energy is required overcome the repulsive force between the two -vely charged particles in order to gain another electron
true of false
1. organic compound is more soluble in hot solvent
2. the hot solution is colled before purified organic compound is collected
3. the mp of purified organic compound is lower than impure compound
- true
- true
- false
what are the reagents to prepare phenlyamine from phenol
dilute HNO3 and then conc HCl/ Sn
whats M+
The molecular ion (M+) is the ion produced when the molecule is ionised by loss of an electron from the molecule
(small peak before the Mr peak)
which statement is incorrect
a. energy from IR causes some covalent bonds to vibrate more
b. absorption of IR by some atmospheric gases is linked to global warming
c. IR is used to monitor gases causing air pollution
d. action of IR on CFCs in upper atmosphere leads to chlorine radicals formation
d. - not true
what happens to H nmr when D2O is used
OH and NH peaks disappear
how do u remove an acid impurity form an organic liquid
add base eg na2co3
why use reflux
prevent any substance from escaping
what does nh3 act as in neutralisation reaction
base
what happens to 1st ionisation energy down the group
decreases since more shielding so less nuclear attraction so less energy required
what are cations and anions
cations-+ve ions
anions- -ve ions
what happens to atomic radius across a period
decreases since same no of shells but greater mass so greater nucleus
how to find the priority group in an alkene
split into left and right- look at each group - higher the Mr= greater priority
