# Topic 6 - Quantative Chemistry Flashcards

How do you work out relative formula mass?

You use this when you have a compound. You add the mass of each element together. If there is two of one then times it by that number before adding it. If there are two elements in brackets you add their mass together before times by how many there are then adding to the other elements.

What is the simple for atomic mass?

A(little r)

What is the symbol for formula mass?

M(little r)

How do you work out the percentage mass of an element in a compound?

Ar x no. Atoms (of that element)

——————————— x 100

Mr (of whole compound)

How do you work out relative atomic mass?

It is the same as the mass number or an element.

How do you find the empirical formula (from masses)

List the elements

write the mass

divide the mass by the atomic mass

Divide the smaller number into each number

multiply to get whole numbers

each number is the number of that element in the compound

What is theoretical Yield?

theoretical yield is calculated yield/maximum amount of product when reactants have completely reacted

Explain why actual yield is usually less than theoretical yield

reaction may be incomplete

product/reactant lost

unwanted reactions

what is the moles formula for solids

moles = mass/atomic mass

How do you work out percentage yield?

actual yield/theoretical yield x 100

Why are lots of waste products a problem?

They aren’t usually commercially useful

If its harmful it can be a threat to people and the environment and disposing of them can be expensive.

What kind of reactions do chemists want?

Ones that safely makes the most profit.

High percentage yield so lots of product is made from the expensive raw materials

All of the products commercially useful.

Suitable speed so the products are make quickly and safely.