Module 1 Flashcards
What are the bonds that hold H2O together?
Dipole-dipole bonds (hydrogen bonds).
Why is Ice less dense than water?
In ice the bonds are rigidly held together, maximising the total number of possible hydrogen bonds- the structure is more open, hence it is less dense than liquid water.
What is it called when water is the solvent?
Hydration.
Why do ions dissolve in solution?
Because solvation (+ve ion being surrounded by negatively charged dipole oxygen of H2O and -ve ion being surrounded by positively charged dipole hydrogens of H2O) help stabilise ions.
What is a polar molecule?
A molecule that has dipoles (large differences in electronegativity between atoms in a bond).
What is water a good solvent for, polar or non-polar molecules? Give examples of types of functional groups
Polar molecules, e.g. Alcohols, Amines, Carboxylic acids, Amino acids.
Do non-polar molecules have a solubility of 0? If not, how so.
Because the permanent dipoles of H2O (due to the electronegativity difference in the bonds of H-O) can induce a dipole in a non-polar molecule (negative O in H2O can repel electrons from an atom in a non-polar molecule, causing the formation of a -ve and +ve dipole).
Define electrolyte.
An electrolyte dissolves to give ions in solution (a non-electrolyte does not give ions in solution e.g. glucose).
Define weak and strong electrolyte.
Weak- partially dissociates into ions.
Strong- fully dissociates into ions.
Why is glucose a non-electrolyte yet can dissolve spontaneously in water?
Because when it dissolves, the molecules are unchanged in their bonding (no ions are formed).
What does Q represent in the equilibrium equation?
Q is the quantified amounts of the reactants
and products present in the reaction mixture over time. (same expression as K - products over reactants).
What does Kc / Kp stand for? and what is the equation for it.
Equilibrium constant. which equals [products] divided by [reactants].
If Q
Reactants are converted into the products until equilibrium is reached (Q=Kc) and the opposite is true if (Q>Kc).
Do pure solids or liquids appear in K expressions? Why?
No, because the concentration of a solid or liquid is constant.
How can you change the pressure of a system?
- Change volume
- Adding an inert gas
What is does Q mean?
Q describes the composition of a reaction at any point during the reaction. (same expression as K - products over reactants).
What needs to be constant for K to be constant?
Temperature.
If K = x for a equilibrium reaction, what does K equal for the reverse reaction?
K for the reverse reaction is the inverse of K for the forward reaction, so K = 1 / x.
What happens if the volume is decreased (increase in pressure) in a gaseous system at equilibrium?
The equilibrium will shift towards the side with a lower number of moles of gas molecules (if both sides have am equal number of moles of gas molecules, no shift will occur). Vice versa - (decrease in pressure - shift towards more gaseous molecules)
What is Qc?
?
What would happen to the position of equilibrium if the temperature was increase in either an exothermic or endothermic reaction?
For an exothermic reaction, an increase in temperature leads to the position of equilibrium moving to the left (less products, more reactants)
For an endothermic reaction, an increase in temperature leads to the position of equilibrium moving to the right (more products, less reactants)
What do catalysts do?
Catalysts help reach equilibrium faster, without being used up in the reaction (not included in equation) and does not change the position of equilibrium.
What is solubility (s) and what does it depend on?
Solubility (s) is a measure of how much solute will dissolve
in a given volume of solvent.
Solubility depends on:
chemical nature of solute and solvent
temperature, T
pressure, p (for gaseous solutes)
What is Ksp?
Ksp, the Solubility Product, is the equilibrium
constant for the dissolution of a slightly soluble salt in
water. (same expression as K - products over reactants, however solids don’t appear in the expression as usual, so the expression is usually just the products).
How can we tell if a precipitate will form?
A comparison of Qsp and Ksp can tell us whether or not a
precipitate will form on mixing aqueous solutions of ions.
If Qsp < Ksp no ppt will form.
If Qsp > Ksp ppt will form.
What is the common ion effect?
The solubility of an ion will decrease in a solution, if some is already present before being added.
What does a lewis acid do and what does a lewis base do?
Lewis acid is an electron pair acceptor.
Lewis base is an electron pair donator.
What is a Brønsted acid and base do?
A Brønsted acid is a proton donor.
A Brønsted base is a proton acceptor.
What is a conjugate acid and conjugate base?
A conjugate acid has accepted a proton.
A conjugate base has lost a proton.
What makes an acid?
An acid is a molecule which contains a proton (hydrogen) attached to an electronegative element in a polar bond. (such as oxygen or a halogen F, Cl, Br, I).
What makes a base?
Molecules that contain an atom with at least one pair of lone electrons usually oxygen or nitrogen.
How are the strongest bases usually formed?
By the deprotonation of molecules containing H-X bonds (hydrogen to an electronegative element), where X is a element from group 15 or 16. (e.g. OH- is a strong base formed by the deprotonation of H2O).
