Moles + Concentration + Gases

Question 1

What is a mole?

Answer 1

the number of molecules in a substance

1 mole = 6.02 x 10^23

Question 2

What is the mole formula wt Avogadro’s number?

Answer 2

n = No/Na

n = # moles
No = # particles
Na = Avogadro's #

Question 3

What is molar mass?

Answer 3

mass of 1 mole
unit = g/mol

the same as relative atomic mass

Question 4

What is the practical mole formula?

Answer 4

n = m/M

n = # moles
m = mass
M = molar mass

Question 5

What is a solute?

Answer 5

a substance that is dissolved in a solvent

Question 6

What is a solvent?

Answer 6

a dissolving medium

Question 7

What is a solution?

Answer 7

a homogeneous mixture of > (or equal to ) 2 substances

Question 8

What is concentration?

Answer 8

measurement of the amount of solute dissolved in a given volume of solvent

Question 9

What are some concentration conversions?

Answer 9

ml = cm3
L = dm3
1L = 1000ml
therefore, dm3 = 1000cm3
1g = 100mg

Question 10

What do brackets around a formula mean?

Answer 10

concentration of

Question 11

What are units for concentration?

Answer 11

g/dm3 = gdm-3

mol/dm3 = moldm-3

comlarity = concentration

Question 12

How is density calculated?

Answer 12

d = mass / volume

therefore unit = g/dm3

Question 13

What is the concentration formula wt moles?

Answer 13

n = cv

n = # moles
c = concentration
v = volume ALWAYS IN dm3!!

Question 14

What is a standard solution?

Answer 14

solution of known concentration known precisely (often to 4 significant figures)

Question 15

How are solutions made from a solid?

Answer 15

1. add known mass of solute to volumetric flask
2. add small amount of water & dissolve
3. add water until bottom of meniscus sits exactly on line
4. calculate concentration
   n = m/M n = cv therefore, m/M = cv

Question 16

How are stock solutions diluted?

Answer 16

water is added to a solution wt a known concentration and unknown value to a solution wt a known volume and known concentration

therefore, # of moles remains the same but water is added

Question 17

What are the formulas for diluted stock solutions?

Answer 17

n = c1v1  (stock solution)
n = c2v2 (desired solution)

therefore, c1v1 = c2v2

Question 18

How is the concentration of ions calculated?

Answer 18

the concentration of an ion in a solution is the concentration of the solution multiplied by however many number of ions are present

Question 19

What is the assumption involving gas calculations?

Answer 19

all gases behave like ideal gases

Question 20

What are ideal gas characteristics?

Answer 20

particles always moving

particles move in straight line until collide wt something

collision = change of direction wt no energy loss = ‘elastic’

no attraction / repulsion btw gas particles

Question 21

What do gases behave like in reality?

Answer 21

under typical conditions (25 C, sea-level pressure) gases tend to behave similarly to ideal gases

increase / decrease temp & pressure increases = deviation from ideal gas behaviour

therefore, gas calculations less valid when applied to scenarios wt decreased temps/ increased pressure

Question 22

What is assumed for the molar volume mass calculation?

Answer 22

if gases are mostly empty space, wt np interaction btw particles

therefore, type of gas molecule should not affect volume

Question 23

What is molar volume?

Answer 23

the same amount of moles of ANY GAS WILL OCCUPY THE SAME VOLUME @ the SAME TEMP & PRESSURE

therefore, only temp & pressure affect gas volume

Question 24

What is STP?

Answer 24

standart temperature & pressure

Question 25

At STP how much does 1 mole of any gas occupy?

Answer 25

22.7 dm3

Question 26

What unit is used for temperature in molar volume calculations?

Answer 26

kelvin

K = x degrees C + 273

Question 27

What is the molar volume formula?

Answer 27

n = v/mv

n = # moles
v = volume (dm3)
mv = molar volume (dm3mol-1)