Chemistry 2017 wjec unit 2 Flashcards
Molecular formula for a straight chained saturated halogenoalkane whos molecules have 50 carbon atoms and 2 chlorine atoms?
c50h100cl2
Explain the effect of increasing temp on the rate of the reaction?
more particles have energy more than activation energy at a higher temp
Structural formula of the monomer?
C double bond C
H3C
Cl
To test for the presence of iodine in an organic compound, the compound?
is first heated with aqueous NaOH
followed by adding excess nitric acid
then aqueous silver nitrate into the mixture
if iodine is present, then a yellow ppt is seen
Catalyst in reaction?
concentrated h2s04
Standard enthalpy change of formation of ethanol?
2C(s) + 3H2(g)+11/2O2 —- C2H50H
Why is difficult to measure the standard enthalpy change of formation of ethanol directly?
If carbon, hydrogen and oxygen - reacted either products would form
Why is it difficult to use this apparatus to determine the enthalpy change of combustion of ethane?
ethane is a gas
Explain the effect that each of the students errors has on the values they obtained?
effect of euan’s error - temp rise / loss in mass is very small so therefore greater percentage error
Effect of carys’error?
mass of fuel used after boiling did not result in temperature rise therefore calculated value of delta combustion H is too small
Standard enthalpy change of formation?
Delta H formation - 1371 = 2 x -394 + 3x-286
delta H formation - 275
-275 kjmol-1
Amir said that hydrogen is the best fuel of these three in terms of the energy released by burning equal masses?
Amir = correct
C= 394/12= 32.8
H2 = 2.86/2.02 - 142
c2H5OH = 13,7.`46 = 29.6
What can be deduced from the fact that 11.2 g reacts exactly with 32g of bromine?
0.2mol of c4h6 and 2 mole of bromine
so 1 double bond
What type of reaction mechanism occurs when X reacts w bromine in the absence of light?
electrophillic addition
What type of reaction mechanism occurs when X reacts with bromine in the presence of sunlight?
free radical substitution
Use spectra to determine the identity of compound Y
use evidence to explain?
IR spectrum
link C-H to 30000 and C-Cl to 650
mass spectrum
Mr= 126/128/130
2 chlorine atoms present from peaks at 35 and 27
13 CNMR
2 different environment
comment on S values
1 HNMR
2 different hydrogen environments
same number of Hydrogens in each environment
1,4 dichlorobutane
Collision theory to explain why the rate
at t - 200
concentration is lower
less frequent collisons
determine if cobalt chloride is a better catalyst than manganese oxide in the decomposition of H202
Measure volume of gas at a particular time
use same amount of catalyst
use same volumes of same concentration of H202
better catalyst increase rate by a inute
Type of mechanism between 2 chlorobutane and potassium cyanide?
nuceophilic subsititution
when 2 chlorobutane is heated, 3 organic products are formed?
but 1 ene
but 2 ene
Z-but-2-ene
What is the type of reaction taking place?
elimination
Why are HFCS preferred to CFCS?
CFCS - destroy ozone layer
more exposed to uv radiation
cfcs produce cl radical
chlorine radical starts chain reaction
HFCS contain H / C-F bonds and these are too strong to be broken by light
How can they get a good yield of pure ethanol?
Needs yeast/enzyme added to mixture
should be kept at body temp
must have some means of allowing co2
produced to escape
distillation needed to separate chain
Calculate atom economy of process as a method of preparing ethanol?
180g of glucose produces 92/180 x 100=51.1%
