Chemistry chapter 4 Acids, bases and neutralisation

Turnbull, 4.1 - 4.3

What is a property of an acid?

Acids are proton donar- which means it is giving out or releasing H+ in an aqueous slution

How is releasing 1H+ion called?

monoprotic

How is releasing 2H+ions called?

diprotic

What is the difference between strong and weak acids?

Fully dissociates which releases all the H+ ions and partially dissociated in water which only release some of the H+ ions into the water.

What are the three examples of a strong acid?

HCl, H2SO4 (sulfuric acid) and HNO3 (nitric acid)

What is an example of a weak acid?

CH3COOH (ethanoic acid)

Define concentration

How many solute is in a solution.

Does a strong acid or weak acid conduct more electricity?

Strong acids, beacuse it release more H+ ions into the solution than a weak acid, allowing more ions to carry the current, conducting an electricity.

What is a property of a base or alkali?

Bases or alkalis are protons acceptors- which means accepting H+ ions to form salt and water.

What is the difference between a base and an alkali?

Bases are insoluble in water which can’t release OH- ions, but will react with acids to form water and salt

Alkalis are soluble in water which can release OH- ions in a solution.

Define neutralisation reactions.

When acids and alkalis react together to make salt and water.

Why titration is need? (3)

1. To determine an unknow concentration for a solution

2. Finding the purity of a substance

3. Find the unknown chemical

Define a standard solution

A solution with a know concentration

Describe why is a standard solution needed?

It is needed to determine the concentration of an unknow solution which can be done by stoichiometry (ratio) and find moles with the equation c= n/v.

How is a standard solution prepared? (5)

1. A solute is weighed on a balance

2. Add the solute to dissolve in a beaker with a bit of distilled water (which needs to be below the band on the volumetric flask)

3. The dissolved solute is then transferred to a volumetric flask with distilled water rinsing the leftovers in the beaker

4. The volumetric flask is then filled up with distilled water up to the bottom of a meniscus

5. A bung is put on the flask and it will be slowly inverted several times to mix the solution thorougly.

Define the meniscus.

The adhesion curve

What are the two most important equipments that is used when carrying out a titration and why.

Pipette that take alkalis and burette that is filled up with acids

These are for accurate liquid volume measurments

Define titre volume.

The volume (that is used up for a neutralisation reaction to happen) obtain from final burette reading subtracting the initial burette reading

What are the procedures for a neutralising reaction happen in a titration. (10)

1. Rinse a pipette with alkali

2. Add a measured volume of alkali to a conical flask with that pipette

3. Add a few drops of indicator to the alkali in the conical flask

4. Place a white tile below it

5. Rinse the burette with acid

6. Fill the burette with acids and record the initial burette reading to the nearest 0.05cm³

7. Release the acid in the burette through the tap into the conical flask and swirl gently

8. Stop the tap when there is a change of colour 

9. Record the final burette reading( read from the meniscus

10. Repeat the titration to get a concordant result (within 0.10cm³) and calculate the mean (the first result will not be considered in the mean)

What are the steps in calculations used to determine the unknow chemical? (4)

1. Find the moles of the unknow chemical with what is given in the question

2. Find the mole the the chemical in the original solution

3. Find the chemical’s molar mass from the moles calculated and mass given ing the question

4. Find the idendity of the unknown acid with the molar mass in the periodic table

How do you find the percentage purity of a substance from titration calculations? (3)

1. Find the moles of the substance and multiply by its Mr to find the mass

2. Then use the mass calculated to divide the mass given in the question

3. Then times by 100 to get a percentage

What is the equation for the percentage uncertainty for a single reading?

absolute uncertainty/ titre(mean value) x100

Define redox.

When oxidation and reduction take place at the same time

Define oxidation

Gain of oxygen and loss of electrons or hydrogen

Define reduction

The gain of electrons or hydrogen and the loss of oxygen

Define oxidation number

Another for oxidation state which is the charge for an ion or the number of electrons that an atom can be accpet or donate.

What is the rule for pure elements in case of oxidation number?

The oxidation number for pure or uncombined elements is always 0

What is the rule for ions and compounds in the case of oxidation number?

Sume of the oxidation state must be the overall charge of that ion or compound.

Do metals have a positive or negative charge in compounds?

positive

Do non-metals have a positive or negative charge in compounds?

negative

Define electronegativity.

The ability of an atom to attract electrons in a chemical bond

How do you determine the electronegativity of an atom according to its position on the periodic table

Electronegativity increases to the right of the periodic table and decrease down the groups.

The strongest is Flourine.

What is knowing the electronegativity of an element helpful?

It is helpful to determine which element is negative or positive in a compound.

What does a more electronegativity atom means?

It shows that that atom will have a more negative oxidation state.

What are the rules for the 3 common combined element in usual cases?

• Oxygen usually have an oxidation number of -2

• Hydrogen usually have an oxidation number of -1

• Flourine usually have an oxidation of -1

What does the roman numerals representsof an element?

Its oxidation number

During oxidation reactions, does the element’s oxidation numbers increase or deacrease?

It increases

During reduce reactions, does the element’s oxidation numbers increase or deacrease?

Decrease

How to write a single half equation? (eg. NO3^1- turning to NO2) (5)

1. Write what you know in the equation and reaction

2. Balance the atoms (not oxygen or hydrogen)

3. Balance the oxygen by adding H2O

4. Balance the hydrogen by adding H+ ions

5. Balance the charge by adding electrons

What are the steps used to combine two half equations? (4)

1. Balance the elements

2. Rearrange the equation by combining both equations

3. cross out any spectator ions

4. rearrange the final equation