Quantative Chemistry(3)

Question 1

What is the law of conservation of mass?

Answer 1

The law of conservation of mass states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants.

Question 2

Define relative atomic mass and relative

Answer 2

Average mass of atoms in an element taking into account masses and abundance of its isotopes, relative to 12C.

Question 3

Define relative formula mass

Answer 3

Sum of relative Atomic Mass of all atoms in the formula.

Question 4

What is Avogadro’s constant?

Answer 4

The number of atoms, molecules or ions in a mole of a given substance. The value of the constant is 6.02 x 10 power of 23

Question 5

What is the formula that links mass, molecular mass and moles together

Answer 5

Mass = Mr x Moles

Question 6

State what we mean by a limiting reactant in a
chemical reaction

Answer 6

In a chemical reaction involving two reactants, it is common to use an excess of one of the reactants to ensure that all of the other reactant is used. The reactant that is completely used up is called the limiting reactant because it limits the amount of products.

Question 7

Write down the two formulae that link concentration, mass/nr moles and volume together.

Answer 7

Concentration (g per dm3(cubed) = Mass (g)/Volume (dm3(cubed)

Concentration (mol per dm3(cubed) = nr of moles/volume (dm3(cubed)

Question 8

What is the molar volume of a gas at room temperature and pressure?

Answer 8

1 mole of a gas at room temperature and pressure occupies 24 dm3

Question 9

What is titration?

Answer 9

A technique for finding the concentration of a solution by reacting a known volume of this solution with a solution of known concentration.

Question 10

How do you conduct a titration?

Step 1

Answer 10

Step 1

Rinse the pipette with a solution of unknown concentration. Use the pipette to measure out the known volume of this solution.

Question 11

How do you conduct a titration?

Step 2

Answer 11

Step 2

Add an indicator (a substance that changes colour at the end of titration)

Question 12

How do you conduct a titration?

Step 3

Rinse the burette

Use a burette to gradually

Answer 12

Step 3

Rinse the burette with a solution of known concentration. Discard the liquid.

Use a burette to gradually add the solution of a known concentration.Discard the liquid.
Use a burette to gradually add the solution of a known concentration.

Question 13

How do you conduct a titration?

Step 4

When indicator changes colour

Answer 13

Step 4

When indicator changes colour (at the end point), the volume added is
recorded

Question 14

How do you conduct a titration?

Step 5

Answer 14

Step 5

It is important to get concordant volume results - they have to lie close to each other

Question 15

How do you conduct a titration?

Step 6

Answer 15

Step 6

Suitable calculations are performed to find the concentration.

Question 16

Why is it not always possible to obtain the theoretical amount of product in a chemical reaction?

Answer 16

● The reaction may not go to completion because it is reversible.

● Some of the product may be lost when it is separated from the
reaction mixture.

● Some of the reactants may react in ways different to the expected
reaction (side reactions may occur).

Question 17

How is the percentage yield of a product in a chemical reaction?

Answer 17

% Yield = Actual mass of a product

                                                                     x100% 

Maximum theoretical mass of product

Question 18

What is atom economy?

Answer 18

A measure of the amount of starting materials that end up as useful products.

It is a ratio of the relative formula mass of desired product to the sum of relative formula masses of reactants.

Question 19

What is atom economy?

Answer 19

A measure of the amount of starting materials that end up as useful products.

It is a ratio of the relative formula mass of desired product to the sum of relative formula masses of reactants.

Question 20

What is the equation that has mass at the top (not in grams)—

Answer 20

Mass

Mole|relative formula mass

Question 21

What is the formula that has number of particels at the top

Answer 21

number of particels particels

Moles X Avagadros constant 6.023 x10(to the power of 23)

Question 22

What is the equation that has moles at the top

Answer 22

Moles

Conc in mol/dm3(cubed)|Volume in dm 3(cubed)

Question 23

What equation has mass in grams at the top (not involving moles and Mr)

Answer 23

Mass (in g)

Conc in g/dm3(cubed)|Volume in dm3(cubed)

Question 24

What does equation has voulme of gas at the top

Answer 24

Voulme of gas

Moles of gas|24dm 3

Question 25

What equation has actual yield at the top

Answer 25

Actual yield

Pecentage yield| theoratical yield

Question 26

What equation has rim of desired product at the top

Answer 26

Rim of desired product

Percentage atom economy| Relative formula mass of all reactants

Question 27

What is relative atomic mass represented as

Answer 27

Ram or Ar

Question 28

What is the relative atomic mass the average mass of

Answer 28

an element compared to carbon-12

Question 29

What does the average mass take into account

Answer 29

The abundance of the naturally occurring isotopes

Question 30

How can the relative formula mass be represented

Answer 30

By (rfm or Mr)

Question 31

Write a balanced equation of magnesium reacting with hydrochloric acid.

Answer 31

Question 32

What is the relative formula mass of:

Answer 32

Question 33

The following reaction occurs in a test tube under a Bunsen Burner:

The carbon dioxide and water escape from the test tube. Use the equation to explain why.

Answer 33

They are both gases

Question 34

Write down the two formulae that link concentration, mole/mass and volume together.

Involves moles

Answer 34

Question 35

Write down the two formulae that link concentration, mole/mass and volume together.

Answer 35

Involves mass

Question 36

What is dimming

Answer 36

It has lots of soot that blocks out the sun