chemistry UNIT 2 recent questions
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how does an oxidising agent change during redox reaction
get reduced : gains electrons and result in decrease in oxidation number
what is the name of compound with formula KClO2
pottasium chlorate (111)
aqous chlorine is added to aqous solution of pottasium iodide the layers are then separated what color is seen in the organic layer
violet
what is the reagent used to test the presence of ammonium ions
NaOH result dap red litmus paper turns blue
exlain why calcium carbonate decompose at higher temp than magnesium carbonate
the ionic radius of magnesium is smaller than calcium which result in a higher charge density even if both have the same charge . so mg will have a greater polarising power to distort the electron cloud of the carbonate bond weakening the bonds more in magnesium than in calcium so less heat energy is needed to break the bonds in mg than calcium CALCIUM has higher thermal decomposition stability than Mg
a methyl oragne indicator is added to a burrete of NaOH then sulfuric acid is added what color is at the end point of tiration
yellow to orange
if there was an air buble between the tap and the tip of the burette will the tirte volume be higher or lower than the accurate titre values
higher than the accurate titre values
what is the Reagent when cyclohaxenol is converted to cyclohexene
concentrated phosphuric (v) acid
explain the trend in electronegativity
down the group there will be greater electronegative as there is greater shielding even though the nucleus charge increases , atomic radius increases as the electrons are further apart from the nucleus it lead to weaker force of attraction between nucleus and electrons as radius is larger and harder to pull the electrons closer to the nucleus
identify by formula a compound produced containing sulfur with its lowest oxidation state for HBr and HI
HBr —-> SO2 HI —->H2S
explain the trend in b.pt of the hydrogen halides
all the hydrogen halides have London forces and permanent dipole-permanent dipole interactions the strength of london forces for the hydrogen halides increase as the number of electrons increase from HCl to HI however in Hf there is alos hydrogen bonding between molecules which is more stronger intermoelcular force than the other 2 listed hence HF has the highest B.PT
give a reson why the reaction of butylamine should be carried by heating the reactants in sealed tube rather than heating under reflux
the ammonia used is a gas if a sealed tube is not used the gas would escape leading to low percentage yield of product and so the reflux has the top part of the condenser opened therfore not used
the reaction between 2 -bromoprapane & potassium hydroxide takes place in 2 diff conditions : in aq and ethanolic compare and contrast these 2 reactions (6)
both reactions involve oh ^- from KOH the reaction in aq solution is a nucleophile substitution while in ethanolic its elemination reaction in the substituition reaction the OH^- acts as a nucleophile while in elimination it acts as a base in the elimination reaction propene is formed while in substituition pron2 ol is formed the equation for nucleophilic substituition is CH3CHBrCH3 + OH^- —-> CH3 CHOH CH3 + Br ^-
give the reasons for the diff between the data book value and experimental value for enthalpy change of combustion
heat loss to the surrounding evaporation of some ethanol incomplete combustion
state 2 standard conditions for the enthalpy change
temperature of 298K pressure of 100 KPa
in which process the hydrogen bonding are broken
H2O (L)—–> H2O(GAS)
Which alkane has the strongest London forces in the liquid phase? (C2H5)4C OR CH3(CH2)7CH3
CH3(CH2)7CH3
What is the total number of structural isomers for cyclic alcohols with the molecular formula C4H8O?
4
In which liquid solvent would the solubility of lithium chloride (LiCl) be lowest?
cyclohexane BECAUSE IT NOT POLAR
Which reaction involves the oxidation of a Group 7 element?
Br2 + F2 → 2BrF
Which test reagent could be used to identify an aqueous solution containing hydrogencarbonate ions, HCO– 3 ?
nitric acid
Which reagent(s) could be used to produce a chloroalkane from a tertiary alcohol? 1 PCl5 2 concentrated HCl 3 concentrated H2SO4 and KCl
1 2 and 3
samples a few drops of calcium and Mg are added to separate test tubes of cold water containing a few drops of universal indicator state and explain the diff in observations made in each experiment (6)