Quantative chemistry

Question 1

What is the law of conservation of mass?

Answer 1

No mass is created or destroyed in a reaction

Question 2

How do you work out the mass of a product from a reaction?

Answer 2

Combine the masses of all the components

Question 3

How do you calculate the mass of a component in a reaction?

Answer 3

Subtract the mass of all other components from the product’s mass

Question 4

When are ionic compounds formed?

Answer 4

When metals react with non - metals

Question 5

What are ions?

Answer 5

Atoms with a charge

Question 6

What type of ions do most non - metals form?

Answer 6

Negative ions

Question 7

Charge of a metal ion is often the same as the ___ ?

Answer 7

Group number

Question 8

Transition metals can form ___

Answer 8

Several ions

Question 9

Which non - metals form positive ions?

Answer 9

Hydrogen and Ammonium

Question 10

What must charges do in an ionic compound?

Answer 10

Cancel out

Question 11

How do you balance a chemical equation?

Answer 11

Look at each atom in the equation and count the amount on either side. Add the correct amount of atoms to either side.

Question 12

What is relative atomic mass?

Answer 12

The weight of an element, taking into account the abundance of each isotope

Question 13

How do we find relative atomic mass?

Answer 13

By adding the masses of all the isotopes (taking into account abundance)

Question 14

What is relative formula mass?

Answer 14

The sum of the relative atomic masses of the atoms in a formula

Question 15

Relative formula mass has no ___ ?

Answer 15

Units

Question 16

Relative formula mass never uses ___ ?

Answer 16

Big numbers

Question 17

How to calculate percentage mass?

Answer 17

Divide relative atomic mass by relative formula mass.

Question 18

What is 1 mole?

Answer 18

1 mole = Relative atomic mass of an element

Question 19

How to work out moles in a compound?

Answer 19

mass (g) / relative formula mass

Question 20

How to work out moles in an element?

Answer 20

mass (g) / relative atomic mass

Question 21

What is avagadro’s contstant?

Answer 21

1 mole (6.02x10^23)

Question 22

How do you use avagadro’s constant to work out the number of atoms in a formula?

Answer 22

• Count atoms in formula
• Calculate amount of moles (weight / relative formula mass)
• Multiply by avagadro’s constant.

Question 23

What is a limiting reactant?

Answer 23

A reactant that get used by before the others.

Question 24

What is an excess reactant?

Answer 24

A reactant that is left over after the limiting reactant has been fully reacted

Question 25

How do you work out the concentration of a solution?

Answer 25

mass/dm3

Question 26

How do you calculate percentage yield?

Answer 26

Work out how many moles of reactant there are (mass/Ar) Multiply amount of moles by product's Ar / Mr to get the product's theoretical mass (product made / theoretical mass) x 100 = percentage yield.

Question 27

Why is it not always possible to achieve 100% yield in a reaction?

Answer 27

Some product may be lost when separated from the reaction mixture Some reactants may react in different ways, producing unexpected results Reversible reactions may not go to completion

Question 28

We cannot achieve _____.

Answer 28

more than 100% yield, as we would otherwise be creating atoms.

Question 29

How do you calculate the number of moles in a volume of a solution?

Answer 29

Divide concentration by volume.

Question 30

How do you calculate the mass of a solution?

Answer 30

Multiply concentration by volume to get number of moles Multiply number of moles by solution Mr to get mass.

Question 31

One mole of any gas occupies of a volume of ____.

Answer 31

24dm^3 at 20c and a pressure of 1 atmosphere.