What is the difference between a group and a period?
Name one element and give the group number and period number.
Group - down the periodic table
Period - across the periodic table
EX. Na - sodium - Group 1 , Period 3
100
Why are the reactions of elements in the same group similar?
Because they have identical outer shells.
100
Define exothermic and endothermic reactions:
Exothermic -> a reaction which produces heat (ΔH has a negative value by convention, -ve)
Endothermic -> a reaction which absorbs heat (ΔH has a positive value by convention, +ve)
100
Hess's Law is:
The law that the evolved or absorbed ______ in a chemical reaction is the same whether the reaction takes one step or several steps. Also known as the law of constant heat summation.
heat
100
Enthalpy changes of reactions are the result of bonds _____ and new bonds _______.
1) breaking
2) forming
200
How does the atomic radius change as you go across the periodic table from left to right?
Increases
increased attractive force (acting on the same energy shell) of the nucleus increases as the number of protons increases
200
Elements on the _____ of the periodic table are metallic while elements on the ____ are non-metallic.
Left
Right
200
Exo or Endo?
Breaking of bonds
Endothermic , energy is required.
200
When a reaction is reversed, what stays the same and what changes?
The sign (+/-) changes.
The magnitude of enthalpy stays the same.
200
Define bond enthalpies:
The energy change when 1 mol of a covalent bond in the gaseous state is formed from its gaseous atoms.
300
How does the electronegativity change as you go across the periodic table from right to left?
Decreases
Less electron attracting power of the larger nuclear charge as we move to the LEFT
300
Rank Bromine, Chlorine, and Iodine in order of reactivity.
Chlorine
Bromine
Iodine
300
What is the value of "c" the specific heat capacity of water? Include units.
4.18 kJ / kg * K
300
What is the intermediate in this reaction:
C (s) + ½ O2(g) → CO (g)
CO (g) + ½ O2(g) → CO2 (g)
C (s) + O2(g) → CO2(g)
CO
300
The enthalpy of a reaction can be found by using bond enthalpies or _____ ____ ______.
Average bond enthalpies
400
From the elements in Group 1:
Name two characteristics that DECREASE down the group.
1) Electronegativity
2) Ionisation Energy
3) Melting Point
400
What is the acid base nature of the Period 3 elements from left to right?
Na - Mg Basic
Al Amphoteric
Si - Cl Acidic
400
What is the definition of a calorie?
Energy it takes to raise the temperature of 1 gram of water by 1 degree Celsius.
400
The energy difference between two states is _______ of the route between them.
independent
400
Why is the reaction between Flourine (F-F) and Ammonia (NH3), exothermic?
Due to the weak flourine-flourine bond in the reactants and the very strong hydrogen to flourine bond (H-F) in the products.
500
Adding the first electron to oxygen is an exothermic process. What process is adding the second electron and why?
Endothermic because even though it is "bond forming", it takes extra energy to overcome the electrostatic repulsion.
500
What are the conditions for a group 1 element to react with a halogen?
Heat
500
What is the change in temperature of a reaction with an enthalpy change of 500 kJ, a mass of 50 kg and a specific heat capacity of 2.5 kJ / kg*K ?
Give an approximate answer.
4 degrees Celsius
500
State Hess's Law.
Hess' Law states that the total enthalpy change between given reactants and products is that same regardless of any intermediate steps (or the reaction pathway).
500
Why does average bond enthalpy give a different end value than enthalpy of formation?
Average bond enthalpy gives an average value while enthalpies of formation are specific to the compounds in question.