Random picks chemistry SQ Flashcards
(95 cards)
1
Q
define molecular ions?
A
when and atom loses or gains an electron it forms ions similarly when a molecule loses or gains an electron it forms molecular ions, N2+ CO+ etc. cationic molecular ions are more abundant than anionic ones
2
Q
how molecular ions are formed?
A
these particles can be generated by passing high energy electronic beams as a particles or x-rays through gas
BREAK DOWN OF MOLECULAR IONS OBTAINED FROM NATURAL PRODUCTS CAN GIVE INFORMATION ABOUT THEIR STRUCTURE.
3
Q
Reliable method for drying crystals?
A
through vacuum desiccator, in this process crystals are spread over a WATCH GLASS and kept in desiccator for several hours. the drying agents used are SILICA GELL, CaCl2, or PHOSPHORUS PENTAOXIDE
crystals are not damaged
shape remains unchanged
4
Q
4 properties of an ideal solvent.
A
- should dissolve large substances at its boiling point and
small ones at room temperature - should not react chemically with the solute
- it should either not dissolve the impurities neither should impurities crystallize along with solute
- on cooling, it should deposit well formed crystals of the pure compound.
5
Q
State Avogadro’s law of gases.
A
equal volume of all the gases at same temperature and pressure containing equal numbers of molecules
6
Q
give 2 examples of Avogadro’s law of gases
A
1 dm3 of H2 gas has a mass = 0.0899g
1 dm3 of Co2 gas has a mass= 1.4384g
7
Q
Define solubility product.
A
(The product of molar solubilities of the ions)
weak electrolyte
at EQUILIBRIUM stage
is called solubility product.
8
Q
DERIVE Solubility product expression for sparingly soluble compound
Ag2CrO4 (silver chromite) inorganic compound.
A
it is denoted by Ksp
Ksp of the salts are very small
quantities and they are temperature dependent.
ion product Ksp
[Ag+]2[CrO4]2 2.6 * 10-(12)
9
Q
Name 4 major parts of apparatus used in LANDSBERGER’s
method for elevation of boiling point?
A
- an inner tube with a hole in it. this tube is graduated
- a boiling flask which sends the solvent vapours into the graduated tube thru ROSEHEAD
- an outer tube, which receives hot solvent vapours from side holes of the inner tube
- a thermometer which can read upto 0.01K.
10
Q
why does evaporation cause cooling?
A
Evaporation cause cooling when
HIGH ENERGY MOLECULES leave liquid and LOW ENERGY MOLECULES are left behind
- the temperature of the liquid falls
- heat moves from surrounding to liquid
- then temperature of the surrounding also falls.
11
Q
define molar heat of fusion
A
The amount of heat absorbed by one mole of solid.
when melts into liquid form at its melting point.
pressure is kept 1atm
12
Q
Define molar heat of Vapourization
A
The amount of heat absorbed when 1 mole of liquid changes into vapours at its boiling point.
pressure during the change is kept 1atm
13
Q
What is transition temperature? 1 example
A
it is the temperature at which 2 crystalline form of the same substance is kept at equilibrium.
example 32.38C
Na2S04 - 10h20 (hydrated form) <— Na2SO4 + 10h20
—> (anhydrous form)
14
Q
4 properties of molecular solids
A
- iodine is one of the best example of molecular ion
2.forces which hold molecules together in molecular crystals:
easily compressible
soft and very weak
- X-rays analysis has shown the regular arrangements of atoms in constituent molecules of these solids, can get exact positions
- mostly volatile, poor conductor of electricity, low melting and boiling points, low densities, sometimes transparent to ight
15
Q
cathode rays as material of nature
A
raw material cant be manufactured.
cathode rays tubes use and interesting assemblage of raw materials.
16
Q
two defects of rutherfords atomic model
A
unstable/ outer electrons could not be in stationary form
unexplained behaviour of electrons
17
Q
Heisenberg’s Uncertainty principle + mathematical expression
A
certainty in the determination of one quantity introduced uncertainty in another quantity.
expression
Δx Δp ≥ h/4π = uncertainty principle.
suppose
x= uncertainty measurement
p= uncertainty momentum
18
Q
molarity
A
number of moles dissolved per dm3 of solution
19
Q
molality
A
number of moles of solute in 1000g =1kg of the solvent
20
Q
salt bridge in voltaic cell function
A
To prevent any net charge accumulation in either beaker by allowing negative ions to leave the RIGHT BEAKER diffuse thru the bridge and enter LEFT BEAKER.
if this diffusional change does not occur the net charge
accumulating in the beakers would immediately stop the flow of electrons and OXIDATION REDUCTION REACTION WOULD STOP.
21
Q
Two advantages of fuel cells
A
- Fuel cells are operated at high temperature, water formed is evaporated
- A number of fuel cells are connected together to obtain several kilowatt power
22
Q
why abnormality of bond length and strength in
HI (hydro-iodic acid) is less prominent than
HCI (hydrogen chloride)
A
chlorine has higher electro negativity than iodine.
so polarities of HCI & HI are un equal
bond length and strength of HCI is more prominent than HI
23
Q
why dipole moment of CO2 is 0 but SO4 is 1.61?
A
because co2 is linear structure, where the dipoles being equal and opposite cancel each other.
S04 is 1.61 D a triatomic molecules having an angular structure with bond angle 104.5°C
24
Q
Why melting point, boiling point, heat sublimation and heat vapourization of ELECTROVALENT (ionic) compounds are higher compares with those of COVALENT compounds
A
due to close packing of oppositely charged ions.
positively charged ions are surrounded by negatively charged ions. thats why.
25
why BF3 is non polar and SO4 is polar
BF3:
trigonal shape, means 3 bonds, cancel each other
a molecule posses bond and still non polar, or positive charge.
ex:
BF3 boron has SP2 hybridization
SO2:
not symmetrical, region of unequal sharing.
the oxygen at bottom of structure is more than negative.
26
Difference between law of conservation + Hess law
LAW OF CONSERVATION OF ENERGY:
energy can not be created or destroyed but can be changed from one to another.
HESS LAW:
independent of path followed by a system
the ENTHALPY change depends upon its INITIAL SYSTEM.
27
why necessary to mention physical states of reactants and products in thermo chemical eq of a reaction
the substances exist because they possess energy.
when a substance changes it also changes its physical state then its energy is also changed.
so in thermochemical reactions it is important to mention physical states of a reaction and products.
28
how surface area affects the rate of reactions? give example.
It increases the possibility of atoms and molecules of reactants to come in contact with each other and the rates enhance.
Example
Al foil reacts with NaOH moderately when warmed BUT
powdered Al reacts with cold NaOH+H2 is evolved in frothing.
2Al + 2NaOH +6H2O -----> 2NaAl(OH)4 + 3H2
29
activation of energy?
The minimum amount of energy required for an effective collision is called activation of energy
30
what is auto catalyst?
in some reactions a product formed acts as a catalyst
this phenomenon is known as auto catalyst.
Ex
when the copper is allowed to react with nitric acid the reaction is slow in the start but eventually it becomes faster. this is due to the formation of nitrous acid during the reaction, which accelerates the rate of REACTION.
31
```
describe 1 mole of H20 has
2 moles of bonds
3 moles of of atoms
10 moles of electrons
and
28 moles of total fundamental.
```
molecule H-O-H has 2 bonds
1 mole of hydrogen contains 2 moles of bond
and 3 moles of atoms.
SIMILARLY there are 8 moles in oxygen and 1 electron is each of the 2 H atoms
1 mole of H2O contains 10 electrons.
total there are 28 moles
10 MOLES OF ELECTRON
10 MOLES OF PROTON
8 MOLES OF NEUTRONS.
32
why concentration HCI and KMno4 solutions can not be filtered by gooch's crucible?
Quick filtration can be done by gooch crucible in a suction filtration apparatus, useful for the filtration of the precipitates which needs to be ignited at high temperature.
If its perforation is covered with ASBESTOS mat then it may be useful for filtration that reacts with paper, eg, concentrated HCI and KMno4 solutions
33
Writes names of major steps involved in crystallization?
The process has following steps
1. choice of solvent
2. preparation of saturated solution
3. filtration
4. cooling
5. collection and washing crystals
6. drying of crystals
7. decolourization of undesirable colours.
34
What do you mean by critical temperature of gases?
temperature of gas in its critical
| which can not be liquefied by pressure alone.
35
absolute zero temperature?
absolute 0, lowest possible temperature, completely at rest.
| Atoms of a substance transfer no thermal heat.
36
Why lighter gases diffuse more rapidly than heavier gases?
Because of greater molecular velocity.
| diffuse faster than heavier ones.
37
solubility product expression for PBcl2 (lead chloride)
denoted as Ksp, salts are in very small quantities.
| soluble in water containing Pb2+ Cl-
38
why change of volume disturbs the equilibrium position but not the equilibrium constant for some gases?
Those gaseous phase reversible reactions.
which happen with changing number of moles are affected by the change of vol at equilibrium stage.
equilibrium position is disturbed but the constant is not.
39
molality is independent but molarity depends upon temperature why?
In molal solutions the mass of the substance and that of the solute are also fixed. not temperature dependent.
In molar solutions we have vol of solutions
vol of a liquid is temperature dependent
SO MOLALITY IS NOT INFLUENCED BY TEMP BUT MOLARITY DOES CHANGE
40
Describe heat sublimation is greater than heat of vapourization.
In sublimation a solid substance is to be directly converted into vapours without melting, high amount of energy is required to overcome inter-molecular forces. on the other hand
vapourization is comparatively low because a liquid substance is to be converted into vapours form. thats why
(like a process is needed)
41
Define lattice energy. with 1 example.
it is the energy released when 1 mole of ionic crystals is formed from gaseous ions. expressed in kJ mole-1
ex
Na+ (g) +Cl- (g) ---------> NaCl
42
Why ice floats over the surface of water?
Ice is less dense than water, causing it to float.
| when something at constant mass increases in volume its density decreases.
43
2 defects of rutherford's atomic model
1. based on laws of motion and gravitation
these laws are not for charged bodies like electrons
2. Atoms should give continuous spectra, but they give line spectra
44
Pauli's exclusion principle
it is impossible for two electrons residing in the same orbital of a poly electron to have same values of hour quantum numbers
```
example
in MG the electrons have opposite spin
|
Mg = [Ne]3s ∨∧
|
```
45
write 2 properties of neutron
1. highly penetrating particles
| 2. can not ionize gases
46
describe that boiling point of a solvent increases due to the presence of solute.
the surface of solute has molecules of solute aswell
They dont allow the solvent to leave the surface as rapidly as in pure solvent.
to boil solutions we need to increase the temperature of solutions in comparison to pure solvents.
47
Recharging of lead accumulator battery.
Commonly used as car battery, it is secondary or storage cell.
passing a direct current, charges it.
charged cell then produces electric current when required.
THE CATHODE OF FULLY CHARGED LEAD ACCUMULATOR IS LEAD OXIDE PbO2 anode is metallic lead.
electrolyte is 30% sulphuric acid.
A SINGLE CELL PROVIDES AROUND 2 VOLTS FOR 12 VOLTS,
6CELLS ARE CONNECTED IN SERIES
48
Electrochemistry
conversion of electrical energy into chemical energy in electrolytic cells.
chemical energy into electrical energy thru galvanic or voltaic cells
49
why an ionic radius is greater than an atomic radius?
creates larger positive charge in nucleus than negative charge
in electron cloud.
causing electron cloud to be drawn a lil closer to nucleus as an ion.
non metal atomic radius is actually smaller ionic rad of same element.
50
electron negativity and electron affinity
Electron negativity
the tendency of an atom to attract a shared electron pair towards itself .
Electron Affinity
it is the energy released when an electron adds to an empty or partially filled orbital of an isolated gaseous atom in its valence energy level to form an anion having a unit negative charge.
51
2 points of valence bond theory
1. in overlapping orbitals electrons become paired with opposite spin to stabilize them.
2. the covalent bond is formed due to the overlap of the partially filled atomic orbitals
52
Ionization energy decreases down the group altho nuclear charge decrease.. why?
Ionization energy decreases inspite of increase in protons number or nuclear charge.
Due to successive addition of electronic shells as a result valence electrons are placed at distance from the nucleus.
As the force of attraction between the nucleus the outer electron decreases with the increase in distance the electron can be removed more easily.
53
External energy of a system?
The energy stored in a substance in terms of its kinetic and potential energy by a virtue of its constituent particles
54
The radio active decay is always a first order reaction. Explain
It has a single species at a moment whose nucleus is being broken upwithout any help of external agency. So only 1 reactant is present and follows the first order mechanism
55
How Mg-atom is twice heavier than C-atom
Atomic mass of mg is 24
| And its twice the atomic mass of C which is 12 that's why
56
How chemical characterization of a compound is done?
A complete chemical characterization of a compound includes both QUALITATIVE and QUANTITATIVE analysis.
▪︎In qualitative analysis
Chemist is concerned with the detection or identification of the elements
▪︎In quantitative the relative amounts of the elements are determined.
57
Solvent extraction and its laws
It is an equilibrium process process and follows the distribution law or partial law.
This law states that the solute distributes itself b/w to immiscible liquids in a constant ratio.
58
why densities of gases are expressed in units of g dm-3 rather than g cm-3? a unit which is used to express the densities of liquid and solids.
if gas densities are expressed in g cm-3 the the values will be very small but when it is expressed in g dm-3 then the value of densities become reasonable to be expressed.
59
derive charles law by kinetic eq of gases
PV= 2/3 kT
derived:
V=2/3 kT/p = 2k/3p (2k/3p) T
at constant pressure
2/3 k/P = k'' (a new constant)
therefore
V/T= k' (charles' law)
60
Molecular mass of gas by general gas eq
if we have any quantity of ideal gas then
THE product of its pressure and volume is equal to the PRODUCT OF NUMBER OF MOLES, general gas constant and absolute temperature.
```
EQ IS REDUCED TO
BOYLES LAW
CHARLES LAW
AVOGADROS LAW
when appropriate variables are help constant
```
PV= nRT when Tn are constant
PV=k BOYLES LAW
V=kT =CHARLES LAW
V=kn AVOGADROS NUMBER
61
HENDERSON'S EQUATION and for what purpose is it used?
henderson's eq shows that 2 factors evidently govern pH of a buffer solution. i.e
pH = pKa + log [salt] / [acid]
the best buffer is prepared by taking equal concentration of salt and acid
pH is controlled by pKa of the acid
62
applications of buffer in daily life.
buffer capacity of a solution is the capability of a buffer to resist change of pH, can be measured quantitatively that how much extra acid or base the solution can absorb before the buffer is destroyed.
63
describe the cleaning actions of soaps and detergents on hte basis of H bonding
carbon chain dissolves in oil and the ionic end dissolves in water.
It forms emulsion in water which helps dissolving dirt when we wash our clothes.
64
isomorphism with 1 example
```
phenomenon in which two different substances exist in the same crystalline form. different substances are called isomorphs.
eg
NaNO3, KNO ----> rhombohedral
cu, ag -----> cubic
zn, Cd -----> hexagonal
```
65
products formed due to decay of neutrons
when electrons are used as projectiles, they carry out the nuclear reactions. A fast neutron ejects an a-particle from the nucleus of nitrogen atom, boron is produced.
14 N + 1n ----> 11B+ 4 He
7 0 5 2
66
give 2 postulates of Plancks theory
energy is not emitted or absorbed continuously.
rather it is emitted or absorbed in a discontinuous manner and in the form of wave packets.
in case of the light, the quantum of energy is often called photon
the amount of energy associated with a quantum of radiation is proportional to the frequency (v) of the radiation
frequency is the number of waves passing through a point per second
E = h v
67
Starks effect
similar splitting of spectral lines.
| when the excited hydrogen atoms are placed in an electrical field.
68
conjugate solution
each liquid layer is the saturated solution of the other liquid.
69
Why NaCl and KNO3 are used to lower the melting points of ice?
because they both have lower the vapour pressure and depress the freezing point of ice.
70
how impure copper can be purified by electrolytic process.
impure copper is made of anode and a thin sheet of pure copper which is made of cathode.
copper sulphate solution is used as an electrolyte
both cu+ cu- converted into Cu2+ ions and migrate to cathode, pure copper.
in this way Cu anode is purified. impurities left at anode.
71
ionic compound do not show the phenomena of isomerism why?
ionic bond is electrostatic. not directional so the compounds do not show the phenomena of isomerism
72
sigma bond is stronger than pi-bond. why?
sigma bond is formed by HEAD TO HEAD approach and electronic cloud density is symmetrically distributed along the bond
pi bond is formed by parallel overlapping of two half-filled p-orbitals.
pi bond is more diffused.
73
ionic and covalent radii
ionic radius
it is the radius of an ion considered spherical in shape
covalent radius
it is half the length of a covalent bond between two atoms
74
enthalpy of neutralization
the amount of heat involved when 1 mole of hydrogen ion from and acid react with one mole of hydroxide ions from a base to form one mole of water
75
enthalpy of combustion
it is the amount of heat evolved when 1 mole of a substance is completely burnt in excess of oxygen. ΔH 0
C
76
catalyst specific in its action. justify
when a particular catalyst works for one reaction, it may not necessarily work for any other reaction.
if different catalysts are used for same reactant then the products may change.
FORMIC ACID IS DECOMPOSED BY Al2O3 to H2O AND CO WHILE Cu CAUSES ITS DECOMPOSITION TO H2 AND CO2
77
homogeneous and heterogenous catalysis
HOMOGENOUS
the catalysts and the reactants are in the same place and reacting system is homogenous. the catalyst is distributed uniformly through out the system.
HETEROGENOUS
the increased surface area of the reactants increases possibilities of atoms and molecules of reactant to come in contact with each other and the rate enhances
78
effect of temperature on energy activation of a reaction
all the molecules of a reactant doesnt posses the same energy at a particular temperature. most of the particles posses average energy. a fraction of total molecules will have energy more than the average energy.
AS THE TEMPERATURE INCREASES NUMBER OF MOLECULES IN THIS FRACTION INCREASES TOO
79
function of electric field in mass spectrometer
also known as electrometer.
| it separates positively charges particles on the basis of mass to charge ratio m/e
80
avogadros number
it is the number of atom, molecules, ions in 1 gram of atoms of an element, one gram mole of a compound, or 1 gram ion of an ionic compound.
81
molar volume
the volume occupied by 1 mole of an ideal gas at standard temperature and pressure -22.414dm3 is called molar volume
82
partition chromatography
the type in which partition of distribution is involved
| eg paper chromatography
83
any two applications of plasma
1. plasma lights up our homes office, distributes light makes our
computers and electric equipment work.
2.drive laser particles, help to clean up environment, pasteurize food and make tools corrosion-resistant
84
law of mass action
the rate at which reaction proceeds is directly proportional to the product of active masses of the reactants
85
how to check the extent of the reaction with equilibrium constant
1. if the equilibrium constant is very large, the reaction is almost completed
2. if value of kc is small, reflects that the reaction doesnt proceeds appreciably in forward reaction
3. if kc value is very small = very little forward reaction
86
why one feels sense of cooling under fan after bath
water particles clinging to our skin evaporate quickly because of fan. when droplets evaporate they take away heat energy from our body.
87
cleavage and cleavage plane
Cleavage
tendency of crystalline material to split
along definite crystallographic structural planes
Cleavage plan
whenever crystalline solids are broken along definite planes
88
Moseley's law + mathematical form
the frequency of a spectral line in X-rays spectrum varies as the square of atomic number of an element emitting it
√v = a (Z-b)
this linear eq is known as moseley law.
89
CuSo4 gives acidic solution when dissolved in water. why?
the solution of 0.2 M solution is 4.0.
| copper (ii) ion reacts with water to make the weak base CuOH- and leaved H+ ions.
90
define oxidation state with 2 examples
it is an apparent charge on an atom OF AN ELEMENT in a molecule or an ion. may be +ve or -ve
1. oxidation state of Mn in KMno4 is +7
2. oxidation state of sulphur in SO2-/4 is +6
91
Enthalpy
total heat content of a substance
| heat change with one mole of sub is dissolved.
92
system and surrounding
system
any portion of universe which is under study
surrounding
the remaining portion other than system
93
half side period
time required to convert 50% of the reactants into products
eg
half time period of decomposition of N2O5 at 45C is 24 minS
94
how law of conservation is applied during stoichiometric calculations.
stoichiometric= balance eq is used
balance chem eq = masses of reactant and products are same
law is applied
95
how many chem reactions take place takes place in surroundings involve the limiting reactant
in our surroundings so many chemical reactions are taking place which involves oxygen.
oxygen always in excess quantity while other reactants act as a limiting reactant
