Module 2: Introduction to Quantitative Chemistry

Question 1

What is the law of conservation of mass?

Answer 1

Matter can’t be created or destroyed
Total mass of products = total mass of reactants
Chemical bonds between atoms are broken, and new bonds are formed

Question 2

what is the difference between and open and closed system?

Answer 2

Closed= a quantity or series of quantities cant enter or leave the system
open= a quantity or series of quantities can enter or leave the system to a significant degree. The mass can change over time

Question 3

What is stoichiometry?

Answer 3

stoichiometry is using a balanced chemical equation to calculate amounts of reactants and products. They are based on the law of conservation of mass.

Question 4

what is a mole?

Answer 4

a unit of measure that helps compare particles of any given substance and its mass
6.022 times 10(power of 23)

Question 5

converting mass formula:

Answer 5

n= m/ MM

Question 6

How do you find number of atoms?

Answer 6

Calculate number of moles
Calculate number of molecules (multiple by Avos. no.)
Calculate no of atoms (times)

Question 7

what is percentage composition formula?

Answer 7

mass/total mass x100

Question 8

what is avogadros number

Answer 8

1 mole = 6.022 × 1023

Question 9

how do you find molar mass?

Answer 9

Find the atomic mass of individual elements
Count how many atoms there are for each element
Add atomic masses together to find MM

Question 10

how do you calculate the empirical formula?

Answer 10

Write down masses of all elements present in a given sample of a compound
Convert masses into moles
Divide by the smallest number of moles to get a simple ratio
If the numbers are not close to whole numbers, multiply by a suitable factor to make them whole numbers
Round off numbers and use them to write the emp. formula

Question 11

Experiment: theoretical value vs experimental value

Answer 11

The experimental value may differ from to theoretical value due to error in the experiment.
We should learn that chemicals react in simple whole number ratios by moles

Question 12

what does the coefficient in front of a balanced chemical equation equal?

Answer 12

the mole ratio

Question 13

what is a limiting reagent?

Answer 13

The reactant that is all used up first is called the limiting reagent because it limits the amount of product that can be formed.

Question 14

what are most solutions measured in?

Answer 14

moles per litre (M)

Question 15

define molarity:

Answer 15

Defined as the number of moles of solute per litre of solution.

Question 16

what is the molarity formula?

Answer 16

C= n/v
n= number of moles
c= concentration in (moles per litre)
v= volume in litres

Question 17

How do you dilute a solution?

Answer 17

we do this by first measuring out a volume of the original solution and adding water to make the new volume. Both solutions have the same number of moles of solute but a different volume. Therefore, they have different concentrations.

Question 18

concentration solution vs diluted solution formula

Answer 18

C2) Concentration of diluted solution x (V2) volume of diluted solution =
(C1) original concentration x (V1) volume of original solution

Question 19

Why are gases so different to liquids and solids?

Answer 19

their volumes are very sensitive to pressure and temperatures

Question 20

Formula for celsius into kelvins:

Answer 20

T(K) = C + 273.15

Question 21

Avogadro’s law:

Answer 21

Equal volumes of gases contain equal numbers of molecules (at same temp and pressure).
One mole of any gas has the same volume (at same temp and pressure).
Because a mole is a fixed number of molecules a mole of any gas has the same volume as the mole of any other gas. This volume is called the molar volume of a gas.

Question 22

Boyles law states:

Answer 22

For a given quantity at a constant temperature, the product of its volume and pressure is constant.
Volume is inversely proportional to pressure.

Question 23

Boyles law formula

Answer 23

p1v1= p2v2

Question 24

Charles law states:

Answer 24

f a given quantity of a gas is held at a constant temperature;
Its volume is directly proportional to the temperature

Question 25

Charles law formula

Answer 25

v1/t1 = v2/t2

Volume (V) is measure in m3 and temperature in kelvin (K)

Question 26

Gay Lussac’s law states:

Answer 26

As the temperature, T, of a gas increases, the pressure, P of the gas increases.
Therefore, P and T are directly proportional.

Question 27

Gay Lussac’s law formula:

Answer 27

p1/t1= p2/t2

The value of (T) MUST be expressed in Kelvin!

Question 28

Ideal gas law formula:

Answer 28

Pv=nrt

Question 29

what does r stand for in the ideal gas law?

Answer 29

R is a constant called the universal gas constant. It is equal to 8.314Jk-1mol-1.

Question 30

Units that must be used in the ideal gas law:

Answer 30

Temp= Kelvin
Volume= litres
Pressure= kPa