Stoichiometric relations

Question 1

what is element ?

Answer 1

1) Single pure substance

2) made of only 1 type of atom.

Question 2

Whats a compound ?

Answer 2

Chemical combination of different elements, containing fixed ratio of atoms.

Question 3

Whats a mixture?

Answer 3

2 or more substances in which no chemical combination has occurred.

1) Elements/ compounds retain their characteristic properties.
2) Composition is not fixed

Question 4

what are homogeneous mixtures?

Answer 4

1) Uniform composition and properties throughout.

Question 5

what are heterogeneous mixtures?

Answer 5

1) Non uniform composition and properties

2) possible to see separate components

Question 6

How can we separate the components of mixture ?

Answer 6

1) Solubility in water, filtration, sand and water
2) Boiling point, fractional distillation, hydrocarbons in crude oil.
3) Magnetism, Iron and sulfur
4) Diff amino acids, net charge at a fixed PH, gel electrolysis.

Question 7

whats sublimation ?

Answer 7

Solid to gas

1) Iodine, CO2 and ammonium chloride goes through sublimation

Question 8

Whats deposition

Answer 8

Gas to solid

1) Formation of snow, frost and hoar frost.

Question 9

Sig Figs in Multiplication and Division

Answer 9

1) Answer should have same number of sig figs as the data value with least no of sig figs

Question 10

Decimal places in Add and subtraction

Answer 10

1) Answer should have the same number of decimal places as the data value with least no of decimal places.

Question 11

What is molar mass

Answer 11

Mass of 1 mole of a substance.

1) Expressed in grams
2) Units= gmol-1
3) Molar mass=M

Question 12

Whats relative atomic mass ?

Answer 12

is the weighed average of 1 atom of an element relative to one twelfth of an tom of carbon 12

Question 13

Empirical formula

Answer 13

Simplest whole no ratio of elements in a compound

Question 14

Link between molar mass and empirical formula mass

Answer 14

X(mass of empirical formula)

Question 15

What is limiting reactant

Answer 15

Reactant that determines the quantity of product.

Question 16

What is theoretical yield ?

Answer 16

refers to the maximum amount of product obtainable assuming 100% of the limiting reactant is converted to product

Question 17

Formula for % yield

Answer 17

percent yield=actual yield/theoretical yield×100

1) helps in determining the efficiency of a process.

Question 18

How does Avogadro’s law relates to gas volumes

Avogardo’s Law

Answer 18

Equal volumes of all gases at same temperature and pressure contain an equal no of particles
V is directly proportional to n

Question 19

What is STP

Answer 19

1) standard temperature and pressure
2) 273 K = 0 Celsius
3) Pressure : 100kPa

Question 20

What is molar volume at STP

Answer 20

22.7 dm3mol-1

Question 21

Formula for no of moles of a gas

Answer 21

Volume/ molar volume

Question 22

Litre is equal to

Answer 22

dm3

Question 23

milliliter is equal to

Answer 23

cm3

Question 24

Kelvin to Celsius conversion

Answer 24

C+273.15

Question 25

1 bar (pressure) is equal to

Answer 25

10^5 Pa

Question 26

What is Boyle’s Law

Answer 26

Pressure of a gas is inversely proportional to its volume

1) PV= constant.
2) Temperate is kept constant

Question 27

What is Charle’s Law

Answer 27

1) Gas volume is proportional to the absolute temperature.

Question 28

Ideal gas equation

Answer 28

PV=nRT

1) P must be in Pa
2) Volume must be in m3
3) T must be in Kelvin.

Question 29

Under what conditions does gas behave like an ideal gas?

Answer 29

1) At low pressure, volume is negligible and there are no attractive forces.
2) High temperature

Question 30

Concentration of a solution

Answer 30

amount of solute (mol) /volume of a solution

Question 31

What are standard solutions?

Answer 31

solutions of known concentrations

Question 32

ppm

Answer 32

1) unit of concentration
2) parts per million
3) Useful in describing low concentrations
4) Each dm3 contains 1mg of solute