S2: Water and Solutions Flashcards
(17 cards)
What shape is water?
Bent
What temperature does water breeze and boil at?
It freezes at 0 degrees celsius and boils at 100 degrees celsius.
Water is more/less dense in the solid phase (ice) compared to the liquid phase (water)?
Less
What does the existence of hydrogen bonding in water result in?
-High MP and BP
-Expansion of water upon freezing
-High latent heat
-High SHC
-Capillary action
-Ability of water to dissolve other substances
Why does water have a high MP and BP?
The strength and number of hydrogen bonds in water and a significant amount of heat energy is required to disrupt these bonds.
Explain why water expands when freezing
As water cools, molecules slow down and begin to adopt a more regular arrangement due to rigid hydrogen bonding between molecules.
The resulting hexagonal lattice in ice pushes molecules further apart than was the case in liquid water, expanding the lattice.
Therefore, the same number of molecules will occupy a larger space and ice has a lower density than water.
What is the latent heat of fusion?
It is the energy required to convert 1 mole of a substance from a solid to a liquid, at its melting point. Latent heat of fusion of water is 6.0kjmol-1
What is the latent heat of vaporisation?
It is the energy required to convert 1 mole of a substance from a liquid to a gas, at its boiling point. Latent heat of vapourisation of water is 44kjmol-1.
What is specific heat capacity and why does water have what it does?
It is the amount of energy required to raise the temperature of 1g of substance by 1 degree celsius. This provides a measure of the substance’s capacity to absorb and store heat energy. When the same quantity of heat energy is applied to two substances with different heat capacities, they will undergo different temperature changes. Water has a relatively high SHC due to capacity for hydrogen bonds to be broken. Water has the value 4.18Jg-1C-1
SHC equation and what unit each part is measured/calculated in
Q=mcdeltat
m = in grams
c = specific heat capacity (water is 4.18Jg-1K-1)
delta t = degrees celsius or kelvin
unit of energy will be in joules
When it says what amount of heat energy would be required to EVAPORATE 200g of water at 100 degrees celsius, what eqn would you use?
Q=n x L (L is latent heat of vaporisation)
When it says what amount of heat energy would be required to MELT 200g of water at 100 degrees celsius, what eqn would you use?
Q=n x L (L is latent heat of fusion)
What is the latent heat of fusion for water?
6.0kj/mol
What is the latent heat of vaporisation for water?
44kj/mol
Difference between molarity and concentration
Molarity = a specific way to express concentration
Concentration is a broad term that includes molarity, ppm, g/L, and more.
Molarity is really just moles of solute per litre of solution
What is the new, unfamiliar way to calculate concentration?
Concentration = amount of solute/amount of solution
1ppm =
1mg/kg in solids and 1mg/L in solutions.
It tells you how many parts of a substance (solute) there are in a million parts of the total mixture or solution.
