Amount of substance

Question 1

What is the value of Avogadro’s constant

Answer 1

6.02 X 10^23 mole^-1

Question 2

What is Avogadro’s constant

Answer 2

It is the number of particles of a substance in one mole of that substance

Question 3

What is the symbol of Avogadro’s constant

Answer 3

NA

Question 4

What is the amount of a substance

Answer 4

The number of moles we have of a substance is called the amount of a substance

Question 5

Symbol of amount of a substance

Answer 5

n

Question 6

What is the unit of amount of substance

Answer 6

Mole

Question 7

What is the symbol of mole

Answer 7

Mol

Question 8

what do scientists call the mass of one mole

Answer 8

The molar mass

Question 9

What is the symbol and unit of Molar mass

Answer 9

Mr

G mol^-1

Question 10

How to calculate molar mass

Answer 10

The molar mass has the same value as the relative atomic mass but the units are g/mol

For a molecule we use the relative molecular mass with the units g/mol

For a giant structure we use the value of the relative formula mass with the units g/mol

Question 11

What is the amount of substance equation

Answer 11

Mass (g)

Amount of substance (mol) =——————————————————————-
Molar mass (g / mol)

Question 12

How can we calculate the number of particles

Answer 12

The number of particles = Amount of substance (mol) X The Avogadro’s constant

Question 13

What is used as a measure of volume in science

Answer 13

The unit decimetre cubed is used ( or known as cubic decimetre {dm^3})

or

Centimetre cubed {cm^3})

Question 14

How can we convert between dm^3 to cm^3

Cm^3 to dm^3

Answer 14

Dm^3 to cm^3 = X 1000

cm^3 to dm^3 = / 1000

Question 15

How can we calculate concentration

Answer 15

Amount of substance (mol)
Concentration (mol/dm^3) = ——————————————-

                                                              Volume (dm^3)

Question 16

What is the volume of one mole of a gas at room temperature and pressure

Answer 16

It has a volume of approximately 24dm^3 at room temperature and pressure

Question 17

What is the value of room temperature

Answer 17

It is considered to be around 20C

Question 18

what is the value of room pressure

Answer 18

101,000 Pa

Question 19

What is the ideal gas equation

Answer 19

pV = nRT

Question 20

What does each symbol stand for in the ideal gas equation

Answer 20

p= pressure (Pa)

V= Volume (m^3)

n= amount of substance (mol)

R= Ideal gas constant

T = temperature (K)

Question 21

How can you calculate from Kilopascal to pascals

Answer 21

X1000

Question 22

Why is pressure changed from kilopascal to pascals

Answer 22

One pascal is actually very low pressure therefore gas pressure is usually originally in Kilopascals (KPa).

Therefore, KPa should be converted to pascals (Pa)

Question 23

Why is m^3 not given in other volumes of either dm^3 or cm^3

Answer 23

One m^3 is a very large volume. Therefore, gas volumes are originally to dm^3 or cm^3

Therefore, the gas volume should be converted to m^3

Question 24

How to convert from dm^3 to m^3

Answer 24

/ 1000

Question 25

How to convert from cm^3 to m^3

Answer 25

/ 1,000,000

Question 26

How to convert from C to K

And from K to C

Answer 26

273 is added to the temperature

273 is subtracted from the temperature

Question 27

What is the value of the ideal gas constant

Answer 27

8.314 J mol^-1 K^-1

Question 28

What assumption are made in the ideal gas equation

Answer 28

We assume that the gas molecules are tiny compared to the spaces between them

We assume that there are no forces acting between the gas molecules

We assume that the gas molecules move randomly

We assume that when the gas molecules collide, the collisions are elastic

Question 29

How can we find the volume of a liquid chemical to determine the molar mass using the ideal gas equation

Answer 29

First we take a gas syringe with a small cap at the end and we use the balance to find the mass of an empty syringe and cap.

Now we remove the cap and draw a small volume of our chemical into the syringe.

We now replace the cap to seal the chemical into the syringe.Next we reweigh the gas syringe containing the chemical plus the cap

Then we calculate the mass of a chemical in the syringe. (Initial mass of empty syringe and cap fro the mass of the syringe containing the chemical and cap)

Now we boil the liquid so it turns into a gas. Therefore, the syringe is placed in a beaker of boiling water.Once it has boiled we read the volume of the gas from the scale of the gas syringe. We then use the volume to work out the molar mass of the chemical (only works for chemical with a boiling point less than 100c as that is the b.p for water. Oil can be used for chemical with a higher b.p)

Question 30

Define the empirical formula

Answer 30

It shows the simplest whole number ratio of the atoms of each element in a compound

Question 31

How can the empirical formula be calculated

Answer 31

Using the molecular formula and dividing all the numbers by the smallest number

Question 32

How can we determine the molecular formula from the empirical formula

Answer 32

We first need to calculate the relative molecular mass of the empirical formula and then multiply it so it becomes the empirical formula mass of the compound.