Energy + Environment 6

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What is the type of bonding for water?
Covalent bonds (electrons shared). OH bonds are polar covalent (electrons tend to oxygen side and hydrogen side positively charged). Bonds intermediate between ionic and covalent (39% ionic).
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What does difference of charge lead to? Why does water have polar charges?
Difference in charge creates electrical dipole. Due to electronegativity (Oxygen attracts electrons more than hydrogen)
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What kind of bonds for what polarity differences?
Large difference in polarity - ionic bonds, small difference - covalent
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What is water structure?
Water has a pyramid shape, with a hydrogen atom at the top, an oxygen atom directly beneath, a hydrogen atom at one corner of the triangle, and 2 lone pairs of electrons making the other corners
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Why does oxygen have 2 lone pairs?
Oxygen has 2 lone pairs as it needs 8 electrons for an outer shell, and it gains electrons from hydrogen.
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Why does water have a net dipole?
Water has a net dipole as oxygen side negatively charged and hydrogen side positively charged. Molecules of polar bonded compounds form weakly bound dipolar structures
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How does water build up it's bonds with other molecules?
Positively charged hydrogen attracted to lone pair
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Why does water have a higher melting and boiling point?
Water has high melting point (0 degrees celsius), and boiling point (100 degrees celsius), and density (1000 kg/m3) compared to methane and other hydrogen compounds due to polar bonds
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Does ice or water have max density?
Density of ice is much less than water, water has a max density of 4 degrees celsius, density then falls beyond this. Ice can thence float on water
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What structure does water have?
Water forms a honeycomb structure with 6 molecules
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What are properties of water?
Very high specific heat (energy to change temperature) - moderates extremes, high surface tension, high latent heat for fusion (melting), and vaporisation (becoming a gas)
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Why is water a good solvent? (good for dissolving)
Salts dissasociate to give positive and negative ions. For NaCl, Cl becomes -ve (ANION) and the hydrogen atoms of water surround it, while for Na, becomes positively charged ( CATION)and the oxygen of water bonds with it.
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What's arrangement in a solution?
Inner hydration shell - chemisorbed, has salt and ordered water around it. Outer hydration shell - cybotactic, semi-ordered. Bulk water is random
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Is water often pure?
Water is very rarely pure
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Why does water have better properties than similar hydrogen bonded structures?
Because of polar bonds, water has a much higher melting point and boiling point compared to ammonia (CH4) mp=- 182, bp= -160, and ammonia (NH3) mp= -78, bp=-33 Hydrogen bonds stronger than Van der Waals
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What does solubility measure? What are states of saturation?
Solubility measures how much a solute can be dissolved in water. Affected by temp and pressure. Unsaturated - can dissolve more, saturated - max dissolved solute, supersaturated - more dissolved than max allowed, precipitate - excess solute comes out
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What affects solubility?
Solubility of gases drops with temperature while for water it increases. Solubility of gases increases with pressure. Henry's law, X(aq) - solubility = k*Px where Px is the partial pressure and k Henry's constant.
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How does the amount of solute affect solubility?
<0.1g/100ml of water - insoluble, 0.1-1 g/100ml of water - slightly solube, 1-10g/100ml - soluble, >10g - very soluble.
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How does NaNO3 dissolve?
Salt still dissolving (unsaturated) -> saturated at dynamic equilibrium -> heating increases solubility so all dissolves after heating from equilibrium -> cooling -> supersaturated as solubility falls -> precipitate forms (dynamic equilibrium)
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Explain the process for salt dissolving?
Salt is put in water, when it begins dissolving some ions precipitate. More dissolve than precipitate. Dynamic equilibrium reached when rate of dissolution equal to rate of precipitation.
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What is solubility product?
Solubility product, Ksp, describes extent of dissolution. for AgCl-> Ag+ + Cl- Ksp= [Ag+]*[Cl-] where the Ag and Cl are concentrations mols/litre
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Calcium fluoride, CaFl2 is added to pure water. Write equation for solubility product
2 Fl (2s) for one Ca, (s). - (s)*(2s)^2 = Ksp
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What is Le Chatelier's principle and example?
Le Chatelier's principle - when equilibrium subject to temp/pressure/concentration change, system reacts to offset change. For reaction N2+3H2-> 2NH3+HEAT, if the solution is cooled, the temperature will want to increase to offset this so NH3 increas
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What is Keq?
Keq is equilibrium constant, indicates the direction of reaction. for a*A (ie- 2C)+b*B -> c*C + d*D Keq= [C]^c*[D]^d/[A]^a *[B]^b where bracketed things are mols/litre
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What does it mean if Keq big?
If Keq is large, this means that the reaction favours products
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Other cards in this set

Card 2

Front

What does difference of charge lead to? Why does water have polar charges?

Back

Difference in charge creates electrical dipole. Due to electronegativity (Oxygen attracts electrons more than hydrogen)

Card 3

Front

What kind of bonds for what polarity differences?

Back

Preview of the front of card 3

Card 4

Front

What is water structure?

Back

Preview of the front of card 4

Card 5

Front

Why does oxygen have 2 lone pairs?

Back

Preview of the front of card 5
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