atoms and reactions

Question 1

What is relative isotopic mass?

Answer 1

The mass of one atom of an isotope compared to 1/12th of the mass of a carbon 12 atom

Question 2

What are isotopes?

Answer 2

Varies of an element that have the same mass number but a different number of neutrons

Question 3

Equation for calculating moles in a solid?

Answer 3

Mass/molar mass

Question 4

Equation for moles in liquid?

Answer 4

Concentration x volume (in dm3)

Concentration x volume…divided by 1000 when in cm3

Question 5

Equation for finding moles in gas?

Answer 5

Volume / 24 (dm3)

Volume / 24000 (cm3)

Question 6

Relative molecular mass?

Answer 6

Weighted mean mass of a molecule compared to 1/12 the mass of a carbon 12 atom

Question 7

Relative formula mass?

Answer 7

Weighted mean mass of a formula unit compared to 1/12 mass of a carbon 12 atom

Question 8

What to do when working out the masses of gases at room temp? For example 1920cm3 C3H8?

Answer 8

Find the volume multiplied by the RMM and then if in cm3 divide by 24,000 and if in dm3 divide by 24
1920 x 44 = 84480
84480 / 24000 = 3.52

Question 9

What to do when finding the volume of a gas at room temperature and only given mass and RMM? For example 1.485g HCN(g)?

Answer 9

Do the mass divided by the RMM - 1.282/64.1 = 0.02

Then multiply by 24 if not given cm3 or dm3 = 0.48dm3

Question 10

Find the mass of potassium hydroxide required to prepare 250cm3 of a 0.200 mol dm-3 solution?

Answer 10

Mol = cv/1000 (volume in cm3)
(0.200 * 250)/1000 = 0.05
Find the RMM of KOH and then multiply by mol
39.1 + 16 + 1 = 56.10.05 = 2.805 g

Question 11

Find the amount in mol of solute dissolved in the following solution, 25.0cm3 of a 0.150 mol dm-3 solution

Answer 11

0.00375mol

Question 12

Concentration in mol dm-3 for 0.500 mol dissolved in 250cm3 of solution?

Answer 12

2mol dm-3

Question 13

Mass concentration in gdm3 for 0.500mol of HCL dissolved in 4dm3 of solution
REMEMBER THIS IS 4dm3

Answer 13

4.5625

Question 14

Acid + Base ->

Answer 14

Salt and water

Question 15

The alkalinity of group 2 hydroxides is used to combat acidity, give two examples?

Answer 15

Ca(OH)2 for lime to neutralise acid soils

Mg(OH)2 for milk of magnesia to neutralise excess acid in stomach

Question 16

What is sodium floride and tin fluoride used for

Answer 16

Toothpaste to prevent tooth decay

Question 17

What are crystals of calcium fluoride used for?

Answer 17

Make lenses to focus infrared light

Question 18

Why do some people not want chlorine in water

Answer 18

May react with organic matter to form chlorinated hydrocarbons which may cause cancer
Peruvians stopped and cholera followed

Question 19

How to work out molecular formula

Answer 19

Find empirical formula
Divide relative molecular mass by relative formula mass
Whatever number produced multiply by empirical formula

Question 20

At room temp and pressure what is the molar volume

Answer 20

24dm3

Question 21

What is a mole?

Answer 21

The amount of any substance containing as many particles as there are carbon atoms in exactly 12 g of the carbon 12 Isotope

Question 22

What is the empirical formula?

Answer 22

The simplest whole number ratio of atoms of each element present in a compound

Question 23

What is a standard solution?

Answer 23

It is a solution of known concentration

Question 24

What is stoichiometry?

Answer 24

The molar relationship between the relative quantities of substances taking part in a reaction

Question 25

What happens when you add ammonia and water together?

Answer 25

NH3 + H2O (equilibrium sign) NH4+ + OH-

Question 26

Why are amino acids amphoretic?

Answer 26

Because they have acidic and basic properties

in amino acid molecule contains a carboxyl acid group and an amino acid group

Question 27

How is a salt made?

Answer 27

any chemical compound formed from an acid

h+ ion from the acid has been replaced by a metal ions or another positive ion such as an ammonium ion

Question 28

What is an example of a diprotic acid?

Answer 28

Sulfuric acid as it has two replaceable h+ ions