C4 chemical calculations

Question 1

What is a proton?

Answer 1

a subatomic particle that has a positive charge and that is found in the nucleus of an atom.

Question 2

What is a neutron?

Answer 2

A subatomic particle that has no charge and that is found in the nucleus of an atom.

Question 3

What is an electron?

Answer 3

A tiny particle with a negative charge. Electrons orbit the nucleus in atoms or ions.

Question 4

What is a nucleus.

Answer 4

the positively charged dense centre of an atom.

Question 5

What is a mass number?

Answer 5

the sum of the number of neutrons and protons in an atomic nucleus.

Question 6

What is an atomic number?

Answer 6

The number of protons (which equals the number of electrons) in an atom. It is sometimes called proton number.

Question 7

What is an isotope?

Answer 7

one of two or more atoms with the same atomic number but with different numbers of neutrons.

Question 8

What is relative atomic mass?

Answer 8

The weighted mean of the relative isotopic masses of an element on the scale where carbon-12 is exactly 12.

Question 9

What is a relative formula mass?

Answer 9

The sum of the relative atomic masses of the elements as given in the formula for any non-molecular compound.

Question 10

What is a mole?

Answer 10

The amount of substance in the relative atomic or formula mass of a substance in grams.

Question 11

What is a reactant?

Answer 11

a chemical substance that is present at the start of a chemical reaction.

Question 12

What is a product?

Answer 12

a chemical substance formed as a result of a chemical reaction.

Question 13

Define a limiting reactant/ reagent

Answer 13

The reactant that gets used up first in a reaction.

Question 15

What is a reversible reaction?

Answer 15

A chemical reaction in which the products re-form the original reactants.

Question 16

Define a yield.

Answer 16

The mass of product that a reaction produces.

Question 17

Define a percentage yield.

Answer 17

The ratio of the actual yield to the theoretical yield, multiplied by 100.

Question 18

What is an atom economy?

Answer 18

The ratio of the relative formula mass of the desired product to the total mass of products, multiplied by 100.

Question 19

What is Empirical formula?

Answer 19

The simplest ratio of elements in a compound.

Question 20

Define a molecular formula.

Answer 20

a chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms.

Question 21

Define concentration (mol/dm3)

Answer 21

The number of moles of a substance divided by the volume of the solution, in dm3 (litres).

Question 22

Define concentration (g/dm3)

Answer 22

The mass of a substance divided by the volume of the solution, in dm3 (litres.

Question 23

What is titration?

Answer 23

A method for measuring the volumes of two solutions that react together.

Question 24

What is a burette?

Answer 24

long glass tube with a tap at one end and markings to show volume of liquid; used to add precisely known volumes of solution in a conical flask below it.

Question 25

What is a pipette?

Answer 25

A glass tube used to measure exact known volumes of solution?

Question 26

What is an end point?

Answer 26

The point in a titration where the reaction is complete and titration should stop.

Question 27

What is the volume of most gasses?

Answer 27

One mole of any gas occupies 24 dm3.

Question 28

Equation for moles?

Answer 28

Moles= mass/Mr or Ar

Question 29

What is the percent composition of an element in a compound?

Answer 29

N x molar mass of element
——————————————. X100%
Molar mass of compound

Question 30

How do you calculate the % yield ?

Answer 30

Actual yield
———————- X100%
Theoretical yield

Question 31

What is the equation for concentration ?

Answer 31

Moles
————-
Volume