Physical - Amount of Substance

Question 1

what is the definition of relative atomic mass?

Answer 1

weighted average mass of an atom of an element, taking into account its naturally occurring isotopes, relative to 1/12 the relative atomic mass of an atom of carbon-12.

Question 2

what is the definition of relative molecular mass?

Answer 2

the mean mass of a molecule of a compound, divided by 1/12 the mean mass of an atom of carbon-12

Question 3

what is relative molecular mass known as for ionic compounds? why?

Answer 3

• relative formula mass
• because they don’t exist as molecules

Question 4

how is number of particles calculated?

Answer 4

moles x Avogadro constant

Question 5

what is the symbol for relative formula mass and relative molecular mass?

Answer 5

Mᵣ

Question 6

what is the definition of the Avogadro constant?

Answer 6

the number of atoms in 12g of carbon-12

Question 7

what is the equation that connects concentration, moles, and volume? include units

Answer 7

concentration (mol dm⁻³) = moles/volume (dm)³

Question 8

state the ideal gas equation

Answer 8

PV = nRT

Question 9

what units must volume be in for the ideal gas equation?

Answer 9

m³

Question 10

how do you convert a value given in cm³ or dm³ to m³?

Answer 10

cm³ = add x10⁻⁶
dm³ = add x10⁻³

Question 11

what units must pressure be in for the ideal gas equation?

Answer 11

Pa

Question 12

how do you convert a value given in KPa to Pa?

Answer 12

x1000

Question 13

what unit must temperature be in for the ideal gas equation?

Answer 13

K

Question 14

how do you convert a value given in ᵒC to K?

Answer 14

add 273

Question 15

what is the empirical formula?

Answer 15

formula that represents the simplest whole number ratio of atoms of each element in a compound

Question 16

what is the molecular formula?

Answer 16

the actual number of atoms of each element in one molecule of the compound

Question 17

what is the stoichiometry of a reaction?

Answer 17

the ratio in which the reactants react and the products are produced in whole numbers

Question 18

what are spectator ions?

Answer 18

ions present in the reaction mixture but are not involved in the reaction - they remain unchanged

Question 19

how do you write an ionic equation from a full balanced equation?

Answer 19

• separate ions in solution into their individual ions
• remove any spectator ions (appear on both sides of the equation)
• check the charges balance

Question 20

what is a standard solution?

Answer 20

any solution where the exact concentration is known

Question 21

what is a standard solution also known as?

Answer 21

volumetric solution

Question 22

how is a standard solution made?

Answer 22

by dissolving a known amount of solid in a known amount of water to create a known concentration

Question 23

why are indicators used in titrations?

Answer 23

change colour exactly when the reaction ends

Question 24

what are the two main indicators used for acid/alkali reactions? give the colours in acid and alkali

Answer 24

• methyl orange (red in acid, yellow in alkali)
• phenolphthalein (colourless in acid, pink in alkali)