C4 Quantative Chemistry

Question 1

What is Avogadro’s constant

Answer 1

The number of atoms, molecules, or ions in a mole of any substance

6.02 x 10^23

Question 2

What is a burette

Answer 2

A tapped, glass apparatus used to add precisely known volumes of liquids to a solution

Question 3

What is concentration

Answer 3

The abundance of solute in a solvent

Question 4

What are concordant readings

Answer 4

Where tire values are within 0.1 cm3 of each other

These precise results can be used in accurate calculations

Question 5

What is the end point

Answer 5

The point in a titration where the reaction is complete

Question 6

What is a limiting reactant

Answer 6

The reactant in a chemical reaction that, when used up, causes the reaction to stop

This reactant is used up first

Question 7

What is a mole

Answer 7

The amount of a substance in the relative mass of the substance in grams

Question 8

What is percentage yeild

Answer 8

The mass of produce collected in a reaction as a percentage of the maximum mass that could have been formed in theory

Question 9

What is a pipette

Answer 9

A glass apparatus used to measure accurate volumes of liquids

Question 10

What is relative atomic mass (Ar)

Answer 10

The average mass of the atoms of an element in comparison to carbon-12

This takes into account the proportions of the naturally-occurring isotopes of the element

Question 11

What is relative formula mass (Mr)

Answer 11

The total of the relative atomic masses, added up in the ratio shown in the chemical formula, of a substance

Question 12

What is titration

Answer 12

A method used for finding the volumes of two solution that react together

Question 13

What is yeild

Answer 13

The mass of product that a chemical reaction produces

Question 14

What is the formula for moles

Answer 14

mass/Ar | mass/Mr

Question 15

How are reactant masses calculated from equations

Answer 15

Find the Mr of the reactant and product in question

Divide the Mr’s by the Mr of the product to find how much reactant forms 1g of product

Multiply this by the amount of product in question to find how much reactant forms it

Question 16

How are product masses calculated from equations

Answer 16

Find the Mr of the reactant and product in question

Divide the Mr’s by the Mr of the reactant to find how much product forms 1g of reactant

Multiply this by the amount of reactant in question to find how much product forms it

Question 17

How are balanced equations written from masses

Answer 17

Find the moles of each substance

Divide each mol by the smallest mol

(If any numbers aren’t integers: multiply all values by the same amount so that they become whole numbers)

Write out the equation with these values in front of their according substances

Question 18

How is product mass found from balanced equations and limiting reactant mass

Answer 18

Find the mol of substance with the known mass

Use the balanced equation to find how many mol of product the limiting reactant can form

Use mol to calculate mass

Question 19

Why is percentage yield always <100%

Answer 19

Reactants may form unwanted products
Product is lost in handling
Reactants may not be pure
Product is lost in separation processes
Products may reform reactants (in reversible reactions)

Question 20

Why is high percentage yield important`

Answer 20

Reduces waste
Uses fewer reactants
Uses less energy
Increases profit
Conserves raw materials
Minimises costs

Question 21

What is atom economy

Answer 21

The mass of the wanted product as a percentage of the mass of all the products

Question 22

How is percentage yield maximised

Answer 22

Using the most efficient reaction conditions and apparatus

Question 23

How is atom economy maximised

Answer 23

Using the most efficient reaction to make the wanted product

Question 24

What is a standard solution

Answer 24

A solution of an accurately known concentration

Question 25

What is the formula for concentration (g/dm3)

Answer 25

solute(g) / solution (dm3)

Question 26

What is a decimeter

Answer 26

1 dm3 = 1000 cm3 To find decimetres, divide cm by 1000 To find centimetres, multiply dm by 1000

Question 27

What happens in a titration

Answer 27

An acid and an alkali neutralise to form a salt and water A known volume of alkali is put into a conical flask with an indicator Acid is slowly added from a burette until the indicator shows that neutralisation has taken place

Question 28

What is a titre

Answer 28

The exact volume of acid needed to neutralise an alkali

Question 29

How is concentration calculated from titre values

Answer 29

Write out the balanced titration equation Calculate the number of moles of the reactant with a known volume and concentration (in burette) Use the equation to find the number of moles for the reactant with a known volume and unknown concentration (in pipette) Use moles and volume to calculate the solution in the conical flask's concentration

Question 30

What is the volume of 1 mole of gas

Answer 30

24dm3 at room temperature and pressure, at 20C and 1 atmosphere

Question 31

How many molecules does gas have under the same conditions

Answer 31

A certain volume of gas contains the same number of molecules under the dame conditions

Question 32

What is the formula for moles of gas

Answer 32

dm3 / 24(dm3)

Question 33

How can the volume of gases be calculated from balanced equations

Answer 33

The ratio of the number of moles in equation gives you the volume of gases involved.