Quantitative chemistry

Question 1

Why is the law of conservation of mass?

Answer 1

no atoms or lost or made during a chemical reaction: mass of products=mass of reactant

Question 2

What is relative formula mass of a compound?

Answer 2

The sum of relative atomic masses of atoms (big number)

Question 3

If a reactant has appeared to change in mass, what has happened?

Answer 3

Reactant or product is a gas and it’s mass isn’t taken into account

Question 4

Why are estimates sometimes necessary?

Answer 4

Because measurements come with uncertainty

Question 5

What are chemical amounts measured in?

Answer 5

Moles - mol.

Question 6

What is the mass of one mole of a substance equal to?

Answer 6

it’s relative formula mass

Question 7

What does one mole of any substance contain?

Answer 7

The same number of particles, atoms, molecules or ions

Question 8

Mass=

Answer 8

moles x relative formula mass
or
concentration x volume

Question 9

Avogadros constant?

Answer 9

6.02 x 10^23 per mole

Question 10

total moles of one elements must be…

Answer 10

the same on both sides of the equation

Question 11

How do you use moles to balance equations?

Answer 11

Convert masses into grams to amounts in moles, convert number of moles to whole number ratios then know how many moles of one elements compared to another

Question 12

What is a limiting reactant?

Answer 12

the reactant that is used up

Question 13

What happens if the limited reactant is used up?

Answer 13

The amount of product produced is restricted to the amount of excess reactant that reacts with the limiting one

Question 14

What is concentration measured in?

Answer 14

g/dm^3 mass per volume of solution

Question 15

Percentage yield?

Answer 15

(amount of product produced/ maximum product possible) x 100

Question 16

Why is it not possible to achieve maximum yield?

Answer 16

Incomplete reactions due to being reversible, some of product may be lost when separated from reaction mixture, some reactants may react in unexpected ways

Question 17

How to calculate theoretical mass of a product given mass of reactant and balancing equation for reaction?

Answer 17

Calculate mol of reactant using mol=mass/ RFM, use balancing numbers to find mol of product, calculate theoretical mass using mass=mol x RFM

Question 18

What is atom economy?

Answer 18

a measure of amount of starting material that ends up as useful products

Question 19

How to find atom economy?

Answer 19

(Mr of desired product from reaction/ sum of Mr of all reactants) x 100

Question 20

What are possible reasons a reaction pathway is or isn’t chosen?

Answer 20

atom economy, yield, rate, equilibrium, usefulness of by products

Question 21

Moles=

Answer 21

concentration x volume

Question 22

What do equal amounts of gases do?

Answer 22

Occupy the same volume under the same pressure and temperature

Question 23

What is the volume of any gas at RTP? room temp and pressure

Answer 23

24 dm^3