CHEMISTRY PAPER 1 Marking Scheme - 2017 MURANG'A MOCK EXAMINATION

1. Water
2. Oxygen is only slightly soluble in water.
3. - Used in welding and cutting metals (oxy-acelytene flame.
  - Used in Hospitals to ais patients with respiratory problems.
  - Metal extraction (To turn ore to oxide:
  - For fuels eg To burn hydrogen to provide energy for space rockets.
1. Fermentation
2. Ethane is non - polar hence does not interact with polar water molecules unlike ethanol which is polar.
1. -1e
2. N = 50 =1.5625
  50 32
  Any other method.
3. Testing absorption of phosphorous from the fertilizer use radio active phosphorus - 31
1. Carbon (IV) Oxide and carbon (ii) oxide
2. Carbon (IV) oxide
  - Fizzy drinks
  - Fire extinguisher
  - Freezing material
    carbon ( II) oxide.
  - As fuel
  - In meta extraction
1. 0.5 x (32 x 60) + 10
  0.5 x 1930 = 965 C
  0.44 965C 88 X 965 = 193 000C
  88g 0.44
  Charge of X =
  1930
  965
  = + 2
2. P(OH)₂

1. 1. r – ethanol
  2. S - chloro ethane
2. T – Dehydration
60 cm³ = 50 sec
80cm³
(^{80 x 50}/₆₀)=66²/₃ seconds
1. Salt Y -1 .At 50^O c only 82g of the 120g salt dissolves.
2. 120 – 82
  = 38g
1. Moisture of water and oxygen/air
2. - Tin coating is non –toxic
  - Tin coating is unreactive
  - Does not corrode easily
1. Add the colourless liquid to anhydrous copper (II) sulphate which colour changes from white to blue
  OR Anhydrous cobalt (II) Chloride which colour changes from blue to pink. ( Any correct)
2. Determine its refractive index
  Determine its density which is 1 g/cm³Determine its boiling point as 100^o C or freezing point as O^o C
1. Copper pyrite (CUFeS_{2 )}
2. CUFeS_{2 (s)}+ Fe₄O_{2 (g)} → CU_{5 (s)} + 2FeO _(s) + 3SO_{3 (g)}
3. Pollute environment due to SO₂gas which causes Acidic rain and can lead to leaching of soil/corrosion of house roof tops .
4. - Making cooking 1 utensils
  - Electrical wires.
  - Making roofing sheets
  - coms and ornaments
  - making alloys
1. Ca and Mg^{2 +}
2. When hardwater is passed through the resin, magnesium 1 or calcium are retained in the resin.
1. staff bridge
2. Fce = E_R−E_{2 =}+ 0.80 −(−0.13 )
  = 0.93V

Conisation energy is the energy required to remove an electron from an atom in gases state while electron affinity is the energy released when an atom in gaseous state gains an electron. ½
CuCO₃ = (⁶⁴/₁₂₄X 100)= 51.61% copper by mass
Alkaline earth metals
1. Magnesium metal conducts due to presence of delocalized elections
2. Molten magnesium chloride conducts since it contains free ions.

1. X – Base ions
2. R
3. T
1. allotrope – Two or more forms of the same physical state of an element existing under standard conditions.
2. Graphite atoms are bounded by covalent bonds to form layers which are held by weak van –derwaals forces making layers slides easily over each other. In Diamond there are only covalent bonds.
1. 100 – 25 = 75 cm³
2. C_XH_y+ O_{2 +} H₂O
  15cm³ 75cm³; 45 = 1: 5: 3
  Hence C_XH_y+ 50_z → 3CO₂+ 4H₂ O
1. Aluminium has more delocalized electrons than sodium making it have strong metallic bonds hence higher melting point.
2. Chlorine molecule is smaller compared to that of sulphur. Thus the van-der-waats forces in chlorine are weaker
1. anhydrons calcium chloride
2. Cooper (II) Oxide turns from Black to brown
3. Hydrogen gas reduces copper (II) oxide to copper metal which is brown.

1. NaCl _(s) + H₂ SO_{4 (aq)} → NaHSO_{4 (s)} + HCl _(g)
2. - React HCl gas with iron to form iron (II)Chloride and hydrogen gas
  - React HCl gas with ammonia gas to form white fumes of ammonium chloride .
3. - Used in large scale manufacture of HCL acid
  - Used in manufacture of polymers such as PVC
The Red litmus paper remains red. This is because dry chlorine gas does not bleach.
By adding aqueous sodium chloride to separate solution of the ions. In case of lead ions (Pb²) ions
White precipitates will be observed while no precipitate form in case of calcium ions.
1. Phenol / phenopthalein indicator 1
2. Acid Base Neutral
  Lemon juice wood ash Sodium chloride

RFM Ca(NO₃)₂ = 40 + 28 + 96 = 164
Thus
164 = 1 mole
8.2 → ? ^{8.2 X 1}/₁₆₄ = 0.05 mole