Solubility, dilutions and pH scale

Question 1

Substances

Answer 1

Water is considered the universal solvent due to its polarity.

Substances that easily dissolve in water are called hydrophilic ionic and polar compounds.
Those that don’t dissolve are called hydrophobic.
Will only dissolve if the energy of the bonds that it forms with water is lower than the energy of the bonds between the water molecules or the bonds within the undissolved substance.

Question 2

Solutions

Answer 2

Saturated: No more solute will dissolve
Supersaturated: Is heated more solute often dissolves if the solute remains in solution as it cools.

Concentration = amount of solute/amount of solvent
Molarity = No of moles/volume in L

Question 3

Mole formula

Answer 3

c = n/v for concentration

n = M/mm for moles

mm is for molar mass and m is for mass

Question 4

Dilutions

Answer 4

Involves diluting down a solution to a bigger volume the moles of the solute don’t change.

C1V1=C2V2

Question 5

Ions in a substance

Answer 5

Ionic bonding involves transfer of electrons to form ions.
Occurs between a metal and non-metal.
Metal loses electrons and become a cation
Non metal gains electrons and becomes an anion
Resulting compound will be electrically neutral due to positive and negative charges balancing out.

Question 6

Polyatomic Ions

Answer 6

May 2 or more atoms will together lose or gain electrons. These can also take part in ionic bonding.

Question 7

Precipitation Reactions

Answer 7

When solutions of certain ionic compounds are mixed they may react producing a solid known as a precipitate.

The result is a solution containing all the ions moving randomly throughout the solvent.
Mixing solutions that contain known cations and anions chemists as have experimentally identified which compounds are solvable and which are insoluble.

Question 8

pH

Answer 8

Acids ionise in solution to produce hydrogen ions. Acids releases hydrogen cations known as protons in an aqueous solution.
Based ionise in solutions to produce hydroxide ions not all bases dissolve in water. Bases either accept a proton, releases a hydroxide anions when dissolved in water alkali.

A strong base or acid will completely dissociate into its ions.

Amphoteric are solutions that act as a base and acid as they both have a transferable H and an atom with line pair electrons. Oxides formed between a metal and oxygen can be basic or amphoteric. Most oxides formed between metal and non metal are acid or natural in solution.

Question 9

Calculating pH

Answer 9

pH =-log(H plus)

A concentration of 1x10^-4M
-log(1x10^-4) = 4pH.

Water dissociates into hydrogen ions and hydroxide ions and they are equal in concentration.

pOH is the amount of hydroxide ions concentrate in a solution if the solutions has a pH of 3 pOH will be 14-3 so 11.

Question 10

Reactions of Acids and bases

Answer 10

Neutralisation: Acid + base = salt and water.

Acid + oxide = salt and water. Acid and ammonia don’t adhere to the generalised reaction because the h ions in attached to the ammonia molecule to produce ammonium ions when it reacts with water it produce hydroxide ions. Considered a weak acid and will react with a base to produce salt water and ammonia gas.

Acids and metals -acid + metals = a salt and hydrogen gas.

Acid + carbonate = salt plus CO2 plus water.

Question 11

Types of equations

Answer 11

Neutral Species: Overall equation for the reaction it shows all reactants and products as neutral compounds.

Complete ionic equation: Shows all ions present in solution. Only special aqueous will split into their ions.

Net ionic equations: Shows only reacting ions no spectator ions.

Question 12

Collisions Theory

Answer 12

For a reaction to occur reactants must collide with sufficient energy at the required orientation. The faster the reaction rate due to more reactants forming products as more often successful collisions occur.

Question 13

Rate of reaction formula

Answer 13

Change in quantity 1/ change in quantity 2

So rise/run

Rate is also change in mass/change in time.

To measure rate of reaction measure pH mass colour volume and concentration.

Question 14

Transition State

Answer 14

As reactants form products brief intermediate stage occurs where the bonds of the reactants have broken but the bonds of products have not yet formed. Temporary unstable structure is called activated complex or transition state. Energy is needed to break the bonds of the reactants so the activated complex has more energy than either reactants or products.

Question 15

Enthalpy

Answer 15

Heat energy possess by a chemical substance. Changing enthalpy between reactants transition states and producers can identify exothermic and endothermic reactions.

Question 16

Activation energy

Answer 16

Amount of energy needed to form the activated complex and is represented by Ea. Needed for reactant bonds to break its the minimum energy required for a reaction to occur. Calculate find the difference in energy between the activated complex and the reactants.

Question 17

Maxwell Boltzmann distribution

Answer 17

At a given temp particles will have different amounts of kinetic energy with the average kinetic energy determining temp.

Factors affecting ROR
Concentration and pressure
SA temperature and catalysts which provide an alternate pathway for reactions which had a lower activation energy for a given temp more molecules will have enough energy to collide.

Question 18

Enzymes

Answer 18

Allows the reaction to occur at an adequate rate is a biological catalyst which means it can participate in a reaction. Large protein molecules highly specific and contain active silo that binds to substrates.

Coenzymes: ions or non protein molecules that change the shape of the active side for the enzyme to function.
Substrate: molecules thats taking part in reaction which enzyme is catalysing.
Active site: area of the enzyme where enzyme contracts directly with the substrate molecule. Upon binding substrate is changed to allow bond to be broken with less energy and therefore increase reaction rate.