[C3] Quantitative chemistry

What is the law of conservation of mass?

No atoms are lost or gained in chemical reactions, therefore the total mass of reactants = the toal mass of the products

How many oxygen atoms are there in O₂?

2

What elements are present in NaOH?

Na = Sodium O= Oxygen H = Hydrogen

What elements are present in CuSO₄?

Cu = Copper S = Sulfur O= Oxygen

What elements are present in BeCl₂ ?

Be = Beryllium Cl = Chlorine

How many atoms of each element are present in BeCl₂ ?

Be = 1 Cl =2

How many atoms of each element are present in CuSO₄ ?

Cu = 1, S = 1, O= 4

How many atoms of each element are present in Be(OH)₂ ?

Be = 1, O = 2 , H =2

How many atoms of each element are present in Ca(NO₃)₂?

Ca = 1, N = 2, O = 6

How many atoms of oxygen are there in 6O₂?

12

How many atoms of each element are there in 3H₂O?

H = 6, O=3

How many atoms of each element are there in 4Be(OH)₂ ?

Be = 4, O=8, H=8

What are isotopes?

Atoms of an element with the same number of protons but different number of neutrons

What is the atomic number?

The number of protons in the nucleus of an atom

What is the mass number?

The number of protons and neutrons in the nuclues of an atom

What is the relative atomic mass (RAM) ?

The average mass of an atom of an element that takes into account the abundance of isotopes

What is the relative formula mass (Mᵣ)?

The sum of the relative atomic masses of the atoms in a molecule or compound

What is the equation used to calculate % mass?

(mass of element in compound ÷ relative formula mass) x 100

What happens to the measured mass when a gas is produced in a chemical reaction?

Measured mass decreases

What happens to the measured mass when a gas is a reactant in a chemical reaction?

Measured mass increases

What is systematic error?

An error caused by a problem with equipment or technique

What is random error?

An error caused by unpredictable variation

What type of error is a zero error?

Systematic error

How can random errors be dealt with?

Do multiple readings and take an average

How can systematic errors be dealt with?

Take new readings using differenet equipment / techniques

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] How many particles, atoms, molecules or ions are contained in 1 mol of a susbtance?

6.02 x 10²³ (Avogadro constant)

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is Avogadro constant?

6.02 x 10²³

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is the mass of one mole of a substance equal to?

The relative formula mass (Mᵣ)

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is a mole?

The amount of substance containing the Avogadro number of particles (6.02 x 10²³).

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is the equation for mole?

"Moles = Mass ÷ Mᵣ

"

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is the equation for mass?

Mass = Moles x Mᵣ

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is a limiting reactant?

The reactant that is completely used up and so limits the amount of product produced

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is a reactant in excess?

The reactant that is not completetly used up in the reaction

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is the mole ratio of this reaction? Mg + 2HCl → MgCl₂ + H₂

1:2:1:1

[𝗛𝗶𝗴𝗵𝗲𝗿 𝘁𝗶𝗲𝗿] What is the mole ratio of this reaction?How many moles of zinc react with hydrochloric acid? Zn + 2HCl → ZnCl₂ + H₂

1 mole of zinc reacts with 2 moles of hydrochloric acid

What is a solute?

A solid that dissolves

What is a solvent?

The liquid in which the solid dissolves

What is a solution?

The mixture formed when a solute dissolves in a solvent

What are the units for concentration?

g/dm³

How many cm³ are there in 1 dm³?

1000

What is the equation used to calculate concentration?

concentration = mass of solute ÷ volume

What is the equation used to calculate mass of solute?

mass of solute = concentration x volume

How can you convert cm³ to dm³?

÷ 1000

How can you convert dm³ to cm³?

x 1000

What is the theoretical yield of a chemical reaction?

The maximum possible mass of a product that can be made in a chemical reaction

What is atom economy?

A measure of how many reactant atoms form a desired product

Why is the percentage yeild usually less than 100 %

• 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

What is the equation for percentage yield?

% Yield = (Mass of product actually made ÷ Maximum theoretical mass of product) × 100

For sustainable development, should reactions with high or low atom economy be used?

High atom economy

What is the equation for atom economy?

(Relative formula mass of desired product from equation ÷ Sum of relative formula masses of all reactants from equation) × 100

What equation is used to calculate concentration in mol/dm³ ?

concentration (mol/dm³) = moles ÷ volume (dm³)

What equation can be used to calculate the moles of a gas?

moles of a gas = volume (dm³) ÷ molar gas volume (dm³)

What is the value for room temperature?

20°

What is the value for room pressure?

1 atmosphere

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

24 dm³