C4.1 - C4.9 Chemical Calculations✔️

Question 1

What is relative atomic mass? Why is it used?

Answer 1

the average mass of its atoms, compared to 1/12th the mass of a carbon-12 atom - is used because the mass of a single atom is so tiny it would be impractical to use

Question 2

How do you work out relative formula mass of a compound?

Answer 2

By adding up all the relative atomic masses of the elements in it

Question 3

Equations for moles?

Answer 3

Number of moles = Mass(g) / Mr

Question 4

Equation for mass(g)?

Answer 4

Mass(g) = number of moles x Mr

Question 5

What is the limiting reactant? What determines the amount of product formend in a reaction?

Answer 5

The reactant that gets used up first in a reaction is called the limiting reactant - the amount of product formed in a chemical reaction is determined by the limiting reactant

Question 6

What is the excess reactant?

Answer 6

The reactant that is not used up is called the excess reactant

Question 7

What is the yeild of a chemical reaction?

Answer 7

Describes how much product is made

Question 8

Percentage yield equation?

Answer 8

% yield = actual mass produced / maxium theoretical mass produced x 100

Question 9

What is a mole?

Answer 9

One mole or mol is simply the relative atomic mass or relative formula mass of any substance expressed in grams - a mole of any substance always contains the same number of atoms this value is called avogadros constant (6.02 x 10^23)

Question 10

Factors affecting the yeild of a chemical reaction?

Answer 10

-product being left behind in the apparatus
-reversible reactions not going to completion
-losses in seperating the products from the reaction mixture

Question 11

Equaion for percentage atom economy?

Answer 11

% atom economy = Mr of desired products from equation / total Mr of the reactants from equation x 100

Question 12

Concentration equation when working with dm^3 ?

Answer 12

Concentration(g/dm^3) = amount of solute(g) / volume of solution (dm^3)

Question 13

Concentration equation when working with cm^3 ?

Answer 13

Concentration(g/dm^3) = amount of solute(g) / volume of solution (cm^3) x 1000

Question 14

What is the end point of a reaction? How do you find it?

Answer 14

The point at which the acid and alkali have reacted completley - you judge when it is reached by using an acid/base indicator

Question 15

What is titration used for?

Answer 15

-Measuring the exact volumes of acid and alkali needed to react with each other

-find the unkown concentration of a solution

Question 16

Number of moles of gas equation when wokring in (dm^3) ?

Answer 16

Number = volume of gas (dm^3) / 24 dm^3

Question 17

Number of moles of gas equation when working in (cm^3) ?

Answer 17

Number = volume of gas (cm^3) / 24,000 cm^3