Elements of the sea

• how does sodium bromide react to form hydrogen halides?

  Reacts with conc sulfuric acid which makes hydrogen bromide. But bromide ions are strong enough reducing agents to reduce the sulfuric aid to sulfur oxide.
• how does sodium fluoride and sodium chloride make hydrogen halides?

  React with conc acid to make hydrogen fluoride or chloride gas. white fumes can be observed as HCl meets moist air. This creates hydrochloric acid. NOT A REDOX REACTION.
• What does fluorine have a low tendency of doing?

  to lose electrons and turn back into atoms so are poor reducing agents.(iodine would be the strongest reducing agent)
• What is fluorine strong at?

  Being an oxidising agent as they have the highest tendency to to be reduced or gain electrons to become fluorine ions.
• how is HCl acid made?

  it can be made as a co product from the chlorination of organic compounds.
• What is the atom economy equation?

  Mr of desired product/Mr of all reactants x100
• What is atom economy?

  The percentage of reactant atoms ending up in the desired productThe greater the atom economy the less waste.
• what is the simplest way to make hydrochloric acid?

  make hydrogen chloride gas by using electrolysis from brine.(100% atom economy)
• What is so special about the sodium thiosulphate titration?

  It isn't an acid base titration instead it relies on using a strong enough oxidizing agent to oxidize the iodide ions.
• Give the steps for the iodine thiosulphate equation


  In bleach excess iodide ions are added to chlorate ions.The iodine produced can be titration using thiosulphate ionsThe end point can be identified by adding starch solution. End point is when the black color disappears.
• Give the equation for the iodine thiosulphate titration second step

  S2O3^2- + 2I —> 2I- + S4O6
• Give the equation for iodine thiosulfate titration first step

  ClO2- + 2I- —> I2 + Cl- +H2O which is brown
• How do you determine the conc of NaCl in bleach?

  Carry out iodine thiosulfate titration.
• Name some uses of chlorine

  Added to water to kill bacteria. Used in household bleach products which remove stains by breaking bonds in colored compounds to form colorless products
• How is chlorine stored?

  In cylinders. The cylinders have to be moved by hoists to avoid damage. A way to check stored cylinders is to take a stick with cloth soaked in conc ammonia solution and a white cloud of ammonium chloride can be seen
• How is chlorine unloaded?

  A scrubber unit ensures that the air being displaced has no chlorine in it.This scrubber has NaOH solution that reacts whith chlorine to produce sodium chlorate- bleach which is then sold on.
• Name some features of the tanks that carry the chlorine.

  They are made of steel.The inside of the tanks are dry as Cl reacts with water to produce corrosive acids.Tanls have cylindrical protective housing on the top to allow unloading and loading.There can be an excess flow valve which closes automatically if the angle valve which regulates the discharge of chlorine is broken.4
• What happens if the temperature or pressure in these tanks becomes too high?

  The tanks have pressure release devices which allow some chlorine gas to be released. this is ok as it is better to release a small amount than a massive explosion of chlorine gas.
• What state is chlorine transported in?

  A liquid as this allows more chlorine to be stored.
• How is chlorine transported?

  by road or rail in pressurized tanks and a warning plate must be used
• name some risks of chlorine?

  it is a toxic gas and can irritate the eyes skin and respiratory system.if inhaled at conc above 40ppm chlorine reacts in lungs to form HCL which affects lung tissue and causes drowning. any leaks of chlorine can be very dangerous.
• Why does chlorine have a poor public image?

  it is associated with pollution through pesticides and it is also a poisonous gas.
• ES5 ...
• What are the rules of determining things about the reaction that involve the Kc value?

  Kc>1 means more products than reactantsKc greater than 10 to the power of 10 means reaction is in completionKc<1 means more reactants than productsKc less than 10 to the power of -10 means reaction has not happened.
• What effects the value of the constant?

  Not effected by concentration change or use of catalyst but is effected by change in temperature this will change position of equilibrium .
• What are the units for equilibrium constant?

  They vary depending on the chemical reaction- mostly just sub in the units into the constant expression and cancel some out.

  
• How do you calculate the equilibrium position?

  The concentrations of the substances in the reaction at the equilibrium position need to be known.It is equal to the concentration of the products divided by the concentration of reactants. any variations in the number of moles raises that substance to a power of the same number of moles.

  
• What is the equilibrium constant Kc?

  This indicates the position of equilibrium for a reaction at a certain temperature. It is always the same value unless the reaction conditions and position of the equilibrium change.
• What does equilibrium graph look like when equilibrium lies in middle.

  
• What does the equilibrium graph look like when it lies to the right?

  
• What does the equilibrium graph look like when it lies to the left?

  
• Give the three points for for definition of dynamic equilibrium

  - concentrations of reactants and products stay constant-forward and reverse reactions are both happening-the rate of the forward and reverse reactions are equal to each other.(the concentrations do not have to stay the same for a reaction to be at dynamic equilibrium .)
• When does a system reach equilibrium?

  When the rate of the forward and backward reaction are equal. reactants are turning into products and products are turning into reactants.
• Describe the reversible reaction for hydrogen iodide.

  H2(g) + I2(g) ---> 2HI(g)if the colourless hydrogen and purple iodine are mixed together in a closed container, the purple colour becomes paler as the iodine reacts and will become constant.
• What does the backwards forwards arrow mean?

  the reaction is reversiblethe forward arrow is the forwards reactionthe backward arrow is the reverse reaction
• What does it mean when a system is at equilibrium?

  The molecules enter and leave at the same rate in bromide it is represented like this Br(l)<-->Br(g)
• What is a reversible change?

  A change that can be undone-thew molecules in bromine can enter the gas phase and then go back into the liquid phase.
• Why is equilibrium dynamic?

  The equilibrium is dynamic because both the forward and backward reactions are still taking place but nothing appears to be taking place- a closed bottle of bromine is in dynamic equilibrium as the orange colour above the liquid remains constant but the particles are constantly moving about and some collide in the liquid and others collide with the gas
• How is chlorine extracted from the sea?

  Chlorine gas is passed through a cold solution of sodium hydroxide which reacts to form sodium chlorate.
• What is chemical equilibrium?

  A state of balance where nothing changes- dynamic equilibrium.