principles of chemistry

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  • Created by: hollie
  • Created on: 22-01-14 10:08
What is meant by catenation?
Is the ablility of an element to bond with itself to form chains or rings.
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why does silicon have much less tendency to catenate?
Silicon does not catenate becasue the Si-Si bond is less stronger than Si-O bonds ( which is very favourable) meaning Si would rather form oxides than catenate
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why can hydrogen fit in group 1 and 17
Hydrogen has 1 valence electron like the group1 metals and is stable as H+. Hydrogen can also fill its 1s orbital and make a hydride H-, halogens are diatomic gases like hydrogen.
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Define matrix
everything else in the sample except the analytes
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define sample
a representative portion of the material to be annalysed
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define analyte
the chemical species to be determined in the sample
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define interferent
anything in the matrix that interferes with analysis
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Whats are the 7 key steps to analytical methodology?
1) formulate the question 2)select the analytical procedure 3)sampling 4) sampling pre-treatment 5)analysis 6) reporting and interpretation 7) drawing conclusions
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define precision
precision describes the reproductibility of a result, and is determined using the standard deviation around a mean (high standard deviation= low precision)
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Define accuracy
accuracy describes how close a measured value is to the true value
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What are the rues for conjugation?
1) 2 double bonds separated by a single bond 2) planar 3)p-orbital overlap
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What are the rules for aromaticity?
1) cyclic 2)planar 3)continuous conjugation 4) (4n+2) pi-electrons
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what are the rules for anti-aromaticity?
1) cyclic 2)planar 3)continuous conjugation 4) (4n) pi-electrons
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How does resonance effect acidity of conjugated molecules?
resonance will increase the stability of the conjugated base therefore increasing acidity becuase the negative charge can be delocalised
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what are the trends of atomic radius in a periodic table?
Down a group it increases, across a period it decreases
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what are the trends of ionisation energy in a periodic table?
Decreases down a group, increases across a period
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what are the trends of electron affinity in a periodic table?
Decreases down a group, increases across a period
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what are the trends of metallic character in a periodic table?
Down a group it increases, across a period it decreases
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What is meant by the inert pair effect?
The reluctance of S electrons towards the bond formation. EG, thallium can exhibit +1 and +3 oxidation states but it stable in the +1 oxidation state only due to the inert pair effect
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Expalin the origins of the diagonal relationship
diagonal relationships occuur because of the directions in the trends of various properties such as atomic radii, charge density and electronegativity (Li&Mg, Be&Al, B&Si)
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How do oxides react in water, and what are the 3 types of oxides?
ionic oxides are basic in water, covalent oxides are acid or neutral in water. 1) basic oxides (Na2O, MgO) 2)amplotetic oxides (Al2O3) 3) acidic oxides (SiO2, SO3, Cl2O)
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How do chlorides react in water?
Ionic chlorides dissolve in water, covalent chlorides are hydrolysed by water
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What are the 3 types of hydrides?
1) molecular hydrides, formed by the electronegative elements ( can be elctron precise,poor or rich) 2) saline hydrides, formed by group 1 and 2 (salt like) 3) metallic hydrides formed by the f&d block
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define gas pressure and state how you measure atomospheric pressure
pressure is define as a force per unit area of the wall of the container (1ATM=101325pa). You use a barometer to measure atomospheric pressure
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How many moles of gas occupies 22.4l at STP
one
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What is an ideal gas?
is a gas that strictly obeys the simple gas laws and has a molar volume of 22.4l
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What is the ideal gas equaiton?
PV=nRT
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How are non-ideal gases different?
MOlecules have repulsion and van der waals, the efffect of size means higher pressure that that of an equivalent amount of ideal gas
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When do real gases act like ideal gases?
at very low pressures and very high temperatures
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Whatr are the equations for gas density?
P=M/V (g/l or Kg/M3) P=MP/RT
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What is the partial pressure equation?
partcial pressure= molar fraction X total pressure
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What are the 3 types of van der waals?
1) orientational forces, have permanent dipoles 2) induction forces, permanent dipole induces dipole 3) dispersion forces, interaction of instantaneous dipoles between non-polar molecules
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What are the types of systems?
1) an open system, interacts with its surroundings by exchange of matter and energy 2) a closed system, exchanges energy but not matter with surroundings 3) an isolated system, exchanges neither matter nor energy with the surroundings
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What is a fucntion of state?
a function of state is a property of the system that has a unque value depending only on the present state of the system eg internal energy
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What happens in exothermic reactions? (delta h < 0)
chemical change in a system is converted to thermal energy. In isolated systems exothermic reaction produce a temperature increase. In a open/closed system they cause heat to be given out to the surroundings
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What happens in a endothermic reaction? (delta h > 0)
thermal energy is converted to chemical energy. In a isolated system they produce a temperature decrease. In a open/closed system they cause heat to be absorbed from the surroundings
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What is specific heat capcity and how do you work out specific heat?
The heat capacity of a system is the quantity of heat required to change the temp of the system by 1 degrees. Specific heat= heat capacity/ mass
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What is enthaply and how do you work it out?
enthalpy is a function of state, H is an extensive property ( depends on the amound of matter in the system) delta H= Hproducts- Hreactants
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Define enthalpy change of reaction
the standard enthalpy change of reaction is the enthalpy change for a reaction in which the reactants in their standard states yield products in their standard states
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define enthalpy change of formation
the standard enthalpy change of formation of a substance is the enthalpy change in the formation of 1 mol of substance for its elements when both products and reactants are in their standard states
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What is entropy and what is the equation to work it out?
The greater degree of disorder is the system the greater the entropy. Standard molar entropy S is the entropy of 1 mole of substance in it standard state. DeltaS=sum of VS(products)- sum of VS(reactants)
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What is free energy and what are the equations?
DeltaG= deltaH-TDeltaS. The standard free energy change of a reaction is the free energy change from reactants to products in their standard states.
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How do you find the equilibrium constant
[products]/[reactants]
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What is the equation for the equilibrium constant and free energy?
deltaG=-RTInK(eq) deltaG0 is endergonic (non-spontaneous)
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What is the van't hoff equation?
InK1= InK2-DeltarH/R (1/T1-1/T2)
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Other cards in this set

Card 2

Front

why does silicon have much less tendency to catenate?

Back

Silicon does not catenate becasue the Si-Si bond is less stronger than Si-O bonds ( which is very favourable) meaning Si would rather form oxides than catenate

Card 3

Front

why can hydrogen fit in group 1 and 17

Back

Preview of the front of card 3

Card 4

Front

Define matrix

Back

Preview of the front of card 4

Card 5

Front

define sample

Back

Preview of the front of card 5
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