Equilibria, Energetics and Elements P 2 – Flashcards
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| In a rate-concentration graph there is a single horizontal flat line, determine the order of the compound |
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| Zero-order with respect to compound |
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| What is the formula for the rate equation? |
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| Rate=k[A]^[B]^ |
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| In a two step mechanism what is the name of the first step? |
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| The rate determining step |
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| What are the reactants in the rate determining step? |
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| The compounds found in the rate equation |
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| Produce a two-step mechanism for this: H2 + 2ICl -> 2HCl + I2 rate=k[H2][ICl] |
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| H2 + ICl -> HCl + HI HI + ICl -> HCl + I2 |
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| Define the term lattice enthalpy |
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| The enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions |
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| State the meaning of the term ligand |
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| Donates an electron to a metal ion / forms a coordinate bond to a metal ion |
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| What is the difference between a strong acid and a weak acid? |
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| A strong acid completely dissociates and a weak acid partially dissociates |
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| Explain what is meant by the term Bronsted-Lowry base |
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| Proton acceptor |
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| Why is it difficult to predict if the lattice enthalpy of magnesium sulfide would be less/more exothermic than that of sodium oxide? |
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| Mg2+ is smaller and Mg2+ has a greater charge S2- is larger But Mg2+ has stronger attraction and S2- has weaker attraction |
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| What is a property of cobalt(II) and cobalt(III) that is typical of transition ions? |
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| They are catalysts or coloured |
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| CoSO4(aq) reacts with NaOH(aq) what is the transition element species formed? And what type of reaction is it? |
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| Co(OH)2 Precipitation |
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| CoSO4(aq) reacts with HCl(aq) what is the transition element species formed? And what type of reaction is it? |
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| CoCl4^2- Ligand substitution |
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| Write an expression for Ka of HNO2 |
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| Ka=([H+][NO2-])/[HNO2] |
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| Ca(OH)2(aq) + HNO2(aq) write the overall equation and ionic equation |
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| Ca(OH)2 + 2HNO2 -> Ca(NO2)2 + 2H2O H+ + OH- -> H2O |
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| How does equilibrium allow a buffer to control pH? |
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| Added alkali reacts with H+ Shifting equilibrium to produce more H+ Added acid reacts with conjugate base(salt) Equilibrium shifts towards HA |
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| What is needed for testing cell potentials? |
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| Voltmeter Salt bridge Electrode (Pt or metal) 1 mol dm^-3 concentration |
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| What are the three ways being developed to store hydrogen for fuel? |
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| Absorption in a solution Adsorption on a solid Liquid under high pressure |
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| Write the equation that links free energy change with enthalpy change and temperature? |
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| /G=/H - T/S |
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| Why could an exothermic reaction occur at low temperatures but not at high temperatures? |
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| T/S is more negative as temperature increases At high temperature T/S is more negative than /H |
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| When is a reaction feasible? |
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| /G<0 or /G=0 |
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| What is the formula for Kc? |
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| [concentration of product]^mol / [concentration of reactant]^mol |
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| What does pressure, temperature and concentrations do to Kc? |
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| Pressure and concentrations do not affect Kc Only temperature affects Kc The system increase/decreases products and reactants to maintain Kc |
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| Define lattice enthalpy |
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| Formation of one mole of an ionic conditions from its gaseous ions under standard conditions |
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| Why do ionic compounds differ in melting points? |
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| There is greater attraction from smaller ions More (heat) energy to overcome attraction |
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| What happens when there is a decrease in entropy? |
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| There is less disorder |
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| If enthalpy and entropy are both negative how will feasibility change as temperature increases? |
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| Reaction becomes less feasible /G increases T/S becomes more negative |
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| How can you work out entropy? |
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| Entropy of products - entropy of reactants |
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| What is the equation for /G? |
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| /G=/H-T/S |
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| When does a reaction become feasible? |
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| /G=0 |
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| Write an expression of Kc for 2CH4->C2H2 + 3H2 |
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| [C2H2][H2]^3/[CH4]^2 |
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| What happens to the initial rate when temperature is increased? |
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| Initial rate increases |
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| What happens to the initial rate when pressure is increased? |
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| Initial rate increases |
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| What happens to the initial rate a catalyst is added? |
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| Initial rate increases |
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| Give two examples of large-scale uses of hydrogen |
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| Fuel cells Manufacture of margarine Making ammonia Making HCl Making methanol |
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| Why would a reaction take place in multiple steps? |
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| Stoichiometry in rate equation does not match stoichiometry in overall equation Collision unlikely with more than 2 ions |
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| Draw a rate concentration graph of something that is first order |
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| [image] |
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| Draw a rate concentration graph of something that is second order |
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| [image] |
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| How do convert pKa to Ka? |
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| 10^-pKa |
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| What are the two general equation for Ka of a weak acid? |
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| Ka= ([H+][A-])/[HA] OR [H+]^2/[HA] |
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| What is the equation for pH? |
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| pH=-log(H+) |
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| Why are Sc and Zn not transition elements? |
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| A transition element has an ion with an incomplete d-orbital Sc and Zn are not transition element Sc3+ is 1s2 2s2 2p6 3s2 3p6 Zn2+ is 1s2 2s2 2p6 3s2 3p6 3d10 Sc3+ d-orbital is empty Zn2+ d-orbital is full |
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| How does H2NCH2CH2NH2 act as a bidentate ligand? |
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| Electron lone pair of N Donates two electron lone pairs to a metal ion |
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| What would make a compound have stronger ionic bonds? |
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| Greater ionic charge Smaller ionic size |
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| What does a y=x rate-concentration graph show? |
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| 1st order with respect |
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| What is the formula for rate equation and what is k? |
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| rate=k[]^order k is the rate constant |
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| How can weak acid be proved by a single pH test? |
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| Measured pH is > 0 |
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| What is the acid dissociation constant? |
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| Ka |
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| What is the formula for Ka of a weak acid? |
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| Ka=([H+]?/[HA]) |
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| What is the relation between the concentration of H+ and pH? |
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| [H+]=10^-pH |
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| What is the equation for Kw? |
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| Kw=[H+][OH-] |
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| What is a buffer formed from? |
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| A weak acid and a salt of the weak acid |
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| What happens when acid is added to a buffer? |
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| Conjugate base reacts with added acid Equilibrium shifts to restore conjugate base (usually left) |
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| What happens when alkali is added to a buffer? |
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| Weak acid reacts with added alkali Equilibrium shifts to restore acid (usually right) |
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| What is needed to set up an electrochemical cell? |
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| Voltmeter Salt bridge Electrodes 1 mol dm-3 solutions in each |
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| What reaction is on the right hand side of the electrochemical cell? |
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| Reduction |
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| How is cell potential worked out? |
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| E(positive terminal (left))-E(negative terminal (right)) |
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| What carries the charge through the wire of an electrochemical cell? |
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| e- |
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| What carries the charge through the solution of an electrochemical cell? |
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| ions |
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| What is the main difference between an electrochemical cell and a fuel cell? |
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| A fuel cell converts energy from the reaction of a fuel with oxygen into a voltage |
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| What is the overall reaction in a fuel cell? |
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| 2H2 + O2 -> 2H2O |
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| What are the ways to store hydrogen? |
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| Under pressure as a liquid Adsorbed on solid Absorbed within solid |
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| Why is the use of hydrogen for fuel considered the same as fossil fuels? |
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| Energy is needed to make the hydrogen |
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| What is the expression for Kc? |
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| Kc=([products]^mol/[reactant]^mol[reactant]^mol) |
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| What side does equilibrium favour when pressure is increased? |
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| The side with the least moles |
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| When pressure increases what happens to Kc? |
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| Kc does not change Increase in pressure causes the system to no longer be in equilibrium So top of Kc expression increases and bottom decreases until Kc is reached |
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| What is another method other than using fossil fuels to produce hydrogen? |
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| Electrolysis of water |
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| What is needed for a reaction to be feasible? |
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| /G < 0 |
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| What is the expression for /G? |
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| /G = /H - T/S |
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| What is the expression for /S? |
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| /S = (sum of products) - (sum of reactants) |
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| If T/S is negative why would an increase in temperature cause a reaction to not be feasible? |
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| As temperature increases T/S becomes more negative Eventually /G becomes positive |
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| What are the two transitional metals with a partially filled 4s sub-shell? |
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| Chromium and copper |
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| What electrons get lost first in transitional metals? |
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| 4s electrons |
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| What is a ligand? |
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| A molecule that donates an electron pair to a metal ion to form a coordinate bond |
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| How can a molecule act as a bidente ligand? |
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| Lone pairs on two atoms Donates two electron pairs Forms two coordinate bonds |
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| What are the three ways to follow the rate of reaction? |
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| Record gas volume Observe colour changes Electrical conductivity changes |
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| What is the reaction rate? |
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| Change in amount of compounds per unit time |
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| What is the half life? |
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| The time its takes for half of the reactant to be used up |
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| What has a constant half life? |
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| First order reaction |
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| What is a clock reaction? |
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| A reaction where you can easily measure the time before a product is formed |
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| What affects the rate constant (k)? |
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| Temperature |
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| A higher temperature does what to the rate constant (k)? |
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| Increases it |
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| How is equilibrium formed? |
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| As reactants get used up forward reaction slows down As more product is formed the reverse reaction speeds up Till the rate of the forward reaction is the same as the reverse reaction |
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| What are the two main things needed for dynamic equilibrium? |
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| A closed system A constant temperature |
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| What is the only thing that affects Kc? |
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| Temperature |
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| Why does temperature affect Kc? |
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| Change means more product is formed Kc will increase |
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| What do cells use as a buffer solution? |
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| H2PO4- H+ + HPO4^2- Dihydrogen phosphate ions and Hydrogen phosphate ions |
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| What does the blood use as a buffer solution? |
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| H2CO3 H+ + HCO3- Carbonic acid |
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| Whats a strong acid/strong alkali titration graph look like? |
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| [image] |
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| Whats a strong acid/weak alkali titration graph look like? |
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| [image] |
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| Whats a weak acid/strong alkali titration graph look like? |
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| [image] |
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| Whats a weak acid/weak alkali titration graph look like? |
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| [image] |
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| The horizontal line of a titration curve indicates? |
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| Equivalence point Neutralised |
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| What is methyl oranges pH of colour change? and what is the colour change? |
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| Red to Yellow 3.1-4.4 |
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| What is phenolphthalein pH of colour change? and what is the colour change? |
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| Colourless to pink 8.3-10 |
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| What are the properties of transition metals? |
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| Form complex ions Variable oxidation states Coloured compounds Good catalysts |
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| What is the colour change that accompanies Cu2+ + 2OH- -> Cu(OH)2 |
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| Pale blue to blue precipitate |
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| What is the colour change that accompanies Co2+ + 2OH- -> Co(OH)2 |
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| Pink to blue precipitate that goes back to pink |
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| What is the colour change that accompanies Fe2+ + 2OH- -> Fe(OH)2 |
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| Pale green to dark green precipitate |
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| What is the colour change that accompanies Fe3+ + 3OH- -> Fe(OH)3 |
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| Yellow to dark orange/brown precipitate |
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| What is a transition element? |
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| Forms a stable ion with an incomplete d sub shell |
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| What is a complex ion? |
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| A transition metal coordinately bonded to one or more ligands |
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| What is a coordinate bond? |
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| Dative covalent bond where a shared pair of electrons come from the same atom |
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| What is a ligand? |
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| A molecule that can donate a pair of electrons to form a coordinate bond |
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| What do you call a ligand with two lone pairs? |
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| Bidentate |
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| What is the structure for platin? |
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| NiCl2(NH3)2 |
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| How is cis-platin used to treat cancer? |
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| Binds to DNA of cancer cell Prevents reproduction |
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| What is the reaction and colour change of aqueous copper(II) ions and ammonia? |
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| [Cu(H2O)6]2+ + 4NH3 [Cu(NH3)4(H2O)2]2+ + 4H2O Pale blue to deep blue |
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| What is the reaction and colour change of aqueous copper(II) ions and chloride? |
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| [Cu(H2O)6]2+ + 4Cl- [CuCl4]2- + 6H2O Pale blue to yellow |
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| What is the reaction and colour change of aqueous cobalt(II) ions and chloride? |
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| [Co(H2O)6]2+ + 4Cl- [CoCl4]2- + 6H2O Pink to blue |
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| What is the reaction and colour change of aqueous cobalt(II) ions and ammonia? |
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| [Co(H2O)6]2+ + 6NH3 [Co(NH3)6]2+ + 6H2O Pink to brown |
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| What does a larger Kstab mean? |
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| Ion is very stable |
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| What is meant by stability constant? |
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| Equilibrium constant for the formation of a complex ions from it constituent ions |
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| Draw the structure of haemoglobin |
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| [image] |
