Quantitative chemistry

Question 1

concentration

Answer 1

It is the number of moles of particles per unit volume (dm3). Unit: mol/dm3

Question 2

1 mole of any gas at room temperature and pressure has a volume of

Answer 2

24 dm3/ 24L

Question 3

Mole

Answer 3

It is a unit used in chemistry. It contains the same number of elementary particles (atoms, molecules, ions) as found in the carbon 12 isotope (C-12). The numerical value of 1 mole is 6.024 x 10^23 (Avogadro’s constant)

Question 4

Zinc always has a charge of

Answer 4

+2

Question 5

A silver ion mostly has a charge of

Answer 5

+1 (can be +2 but rare)

Question 6

isotopes

Answer 6

Isotopes are atoms of the same element that have the same atomic number (protons) but different mass numbers (different neutron numbers)

Question 7

proton= nucleon

Answer 7

Any particle found in the nucleus. A proton is a positive nucleon and a neutron is a neutral nucleon.

Question 8

mole =

Answer 8

mass (m) / molar mass (Mr)

Question 9

Any equation must be balanced to satisfy 3 conservation laws

Answer 9

Mass
Atoms
Charge

Question 10

Empirical formula

Answer 10

The simplest ratio in which elements in a compound combine.

Question 11

relative mass of a single atom

Answer 11

The mass number of that atom (the number of protons plus the number of neutrons)

Question 12

chlorine average relative mass

Answer 12

(75% x 35)+ (25% x 37) / 100= 35.5

Question 13

Relative atomic mass

Answer 13

The average mass of atoms of that element taking into account the mass and amount of each isotope it contains on a scale where the Mass of a carbon 12 atom is 12.

Question 14

Relative formula mass

Answer 14

It is the sum of the relative atomic masses of all the atoms shown in the formula - formula mass.

Question 15

In order to convert mol/dm3 to g/dm3, what do you have to do?

Answer 15

Multiply the concentration by the Mr.

Question 16

spectator ions

Answer 16

remain the same before and after. It is an active ion.

Question 17

Mole

Answer 17

measurement of the amount of a substance

Question 18

Avogrado constant

Answer 18

the number of atoms, molecules or ions in one mole of a given substance (the value of the Avogadro constant is 6.02 x 10^23)

Question 19

When you have a mole of Carbon 12 atoms, you have?

Answer 19

12 of the,

Question 20

One mole contains the same number of atoms, molecules or ions as

Answer 20

one mole of any other substance

Question 21

The value of the Avogadro constant was chosen so that

Answer 21

the mass of one mole of that substance is equal to the relative formula mass (Mr) in grams.

Question 22

Mass (g)=

Answer 22

Mr x Moles

Question 23

What does the volume of a gas vary with?

Answer 23

temperature and pressure

• the higher the temperature of a gas, the greater its volume
• the greater the pressure of a gas, the smaller its volume

Question 24

However, providing the temperature and pressure of gases are the same, equal numbers of moles of all gases have

Answer 24

the same volume

Question 25

What is the volume of any gas at room temperature (20 degrees) and pressure (1 atm)?

Answer 25

It is 24 dm3, th same volume as 24 litres or 24000 cm3

Question 26

volume (dm3) =

Answer 26

24 x moles

Question 27

Why can we use the molar ratio?

Answer 27

Due to equal amounts of moles of different gases having the same volume (at the same temperature and pressure).

Question 28

How can mass be converted into moles?

Answer 28

mass= Mr x moles

Question 29

concentration (g/dm3)=

Answer 29

mass dissolved (g)/ volume (dm3)

Question 30

concentration

Answer 30

It is the number of moles of solute dissolved in each 1dm3 of solution.

Question 31

concentration (g/dm3)=

Answer 31

Mr x concentration (mol/dm3)

Question 32

What are titrations?

Answer 32

Titration is a method/procedure by which a volume of an acid/alkali chemically react to determine the unknown volumes of an acid or alkali.

Question 32

What are titrations?

Answer 32

Titration is a method/procedure by which a volume of an acid/alkali chemically react to determine the unknown volumes of an acid or alkali.

Question 33

Give differences between a biurette and a pippette?

Answer 33

Biurette: It is a high resolution instrument that can be used to measure fixed/ varying volumes of a liquid (controlled by a tap/ stop cock). The resolution is 0.1 cm3/ ml. The zero value is at the top.
Pipette: It is a measuring instrument that could measure a fixed volume of a liquid depending on it’s capacity.

Question 34

What does the law of conservation of mass state?

Answer 34

• The Law of Conservation of Mass states that no matter is lost or gained during a chemical reaction.
• Mass is always conserved, therefore the total mass of the reactants is equal to the total mass of the products, which is why all chemical equations must be balanced
• The sum of the relative atomic/molecular masses of the reactants will be the same as the sum of the relative atomic/molecular masses of the products

Question 35

What is a precipitation reaction?

Answer 35

One in which two solutions react to form an insoluble solid called a precipitate