Atoms and reactions

Question 1

Changing atom

Answer 1

-Dalton- atoms smallest thing, can’t be broken
-JJ Thompson- discovered electrons, plum pudding model
-Rutherford- a particles fired at gold sheet, mass condensed in nucleus with electrons orbiting
-Chadwick- discovered neutron

Question 2

Relative atomic mass-
Relative isotopic mass-

Answer 2

-weighted mean mass of an atom of an element compared to 1/12 of the mass of carbon 12
-mass of an atom of an isotope compared with 1/12 of the mass of carbon 12

Question 3

Mass spectrometry

Answer 3

-used identify unknown compound
-find relative abundance of isotope of element
-determine structural information about molecules

Question 4

Molecular ions

Answer 4

NH4+
OH-
NO3-
CO3 2-
SO4 2-

Question 5

Avagadro’s constant

Answer 5

-number of atoms per mole of carbon 12
6.02 x10 ^23

Question 6

Empirical formula-
Molecular formula-

Answer 6

-simplest whole number ratio of atoms of each element present in a compound eg. C2H6 = CH3
-numbers and types of element in each compound

Question 7

Gas volumes

Answer 7

• one mole of gas occupies 24dm3 = 24000cm3
  mole= volume/24 or 24000

Question 8

Ideal gas equation

Answer 8

pV=nRT
pressure= pascal
volume= m3 = x10^6 cm3
temperature= kelvin 0 C = 273K

Question 9

Make standard solution

Answer 9

-use weigh by difference to weigh solute
-completely dissolve solute in solvent in a beaker
-transfer into a volumetric flask, rinsing beaker and adding to flask
-add solvent to flask but not to graduation line
-add dropwise to the line until meniscus sits on line
-place lid and invert couple times

Question 10

Standard solution

Answer 10

have a known concentration and used to find concentration of unknowns via titration

Question 11

Giant structures examples

Answer 11

-ionic compounds eg. NaCl, CaCl2
-giant covalent structures eg. SiO2
-all metals
-some non-metals eg. carbon, silicon, boron

Question 12

Why % yield is never 100%

Answer 12

-reaction may be at equilibrium not completion
-side reactions may occur
-reactants may not be pure
-some reactants or products left behind in apparatus
-separation and purification may cause loss of product

Question 13

Acids

Answer 13

-pH less than 7
-proton donor as H+ dissociates
-strong acids fully dissociate, weak acids partially

Question 14

Bases

Answer 14

-common bases metal oxides/hydroxides eg. MgO, NaOH
-NH3 and amine= CH3NH2
-opposite of acid, proton acceptor
-neutralise acids

Question 15

Alkali

Answer 15

-pH greater than 7
eg. NaOH, KOH, NH3
-special type of base that dissolves in water releasing OH-

Question 16

Salts

Answer 16

-ionic compound with positive ion eg. metal ion, NH4+ and negative ion from acid
acid + metal -> salt and hydrogen
acid + metal oxide/hydroxide -> salt + water
acid + metal carbonate -> salt + water + CO2
acid + alkali -> salt + water

Question 17

Ammonium salts equation

Answer 17

eg. NH3 + HNO3 -> NH4NO3 (ammonium nitrate)

Question 18

Determine formula of hydrated salt eg. MgSO4 xH2O

Answer 18

-calculate mol of anhydrous salt
-calculate mol of water by subtracting mass of hydrated by anhydrous salt
-use molar ratio and divide by smaller number to get ratio of water

Question 19

Colour in acid, base, end point of titration
Methyl orange
phenolphthalein

Answer 19

Methyl orange
Acid- red, Base- yellow, End point- orange
Phenolphthalein
Acid- colourless, Base- pink, End point- pale pink

Question 20

Oxidation numbers

Answer 20

• element= 0
  -ion = charge
  -oxygen= -2
  -oxygen in peroxides = -1 (H2O2)
  -hydrogen = +1
  -metal hydride = -1 (LiH)

Question 21

Redox equation oxidation numbers

Answer 21

-if increases eg. 0-> +2 = oxidation
-if decreases eg. 0-> -2 = reduction