Quantitative
Define the following term:
Mole
Relative Molecular Mass
Relative Atomic Mass
Mole - amount of substance in a compound or 6.02 x 1023 number of particles .
Relative Molecular Mass - ratio of the mass of the molecule of a substance.
Relative Atomic Mass - mass relative to a C-12 atom and has no unit.
Define Acids and Bases
Acids are proton donors Bases are proton acceptors.
Define the following terms:
Homologous series
Functional group
a group of organic compounds differe by-CH2-
a group of atoms that determines the chemical behavior of an organic compounds
Define the following terms:
Hard water
Soft water
deliquescence
high amount of Ca ions and Mg ions present
few amount of Ca and Mg ions
absorption of water from the atmosphere.
Draw the structure of Magnesium ion
Draw it on the board
Find the Percentage of Oxygen in Nitric Acid, HNO3
M(H) = 1g/mol M(N) = 14 g/mol M(O) = 16 g/mol
M(HNO3) - 63 g/mol
3 x 16 = 48 so 48/63 x 100 = 76.19%
Describe features of an exothermic reaction and state an example.
Heat of the surrounding increases, Releases heat energy, negative enthalpy change, bond-forming
Respiration, Combustion of Methane, Burning wood.
List any 2 uses of ethanol and state 2 properties of alkenes.
Ethanol is used for fuel and as solvents.
Alkenes are insoluble in water and are colorless.
Define allotrope and name two allotropes of Sulfur.
different form of elements in the same physical state.
Monoclinic and Rhombic
Draw the Lewis structure of Ammonia
Trigonal pyramidal shape.
Vitamin C has a mass composition of 40.92% carbon, 4.58% hydrogen and 54.50% oxygen. Calculate the Empirical formula for vitamin C.
m(C)= 40.92g, m(H)= 4.58g, m(O)= 54.50g
M(C) = 12g/mol, M(H) = 1g/mol, M(O)= 16g/mol
n(C)= 40.92/12= 3.408mol, n(H)= 4.58/1.01 = 4.53mol, n(O)=54.50/16= 3.41mol
3.408/3.408 = 1, 4.53/3.408= 1.329, 3.41/3.408= 1
1:1.329:1 since we are looking for the simplest mole ratio multiply by 3
3:3:4 - C3H4O3
On the set of axes on the right, draw an energy profile diagram for the progress of an exothermic reaction. Show and label clearly all of the following:
a) ‘Energy’ axis and ‘Reaction progress’ axis
b) ‘Energy of reactants’ and ‘Energy of products’
c)Enthalpy Change.
refer to word document
Draw the structure of propyne
C3H4
Give two uses of Carbon Dioxide
Photosynthesis and Fire Extinguishers.
Define metallic bond and account for why iron nails gets flattened when hammered.
A metallic bond is a type of chemical bonding that occurs between metal atoms. It is characterized by the sharing of delocalized electrons among a lattice of positively charged metal ions.
Iron nails flattened easily because of the metallic bond that has characteristics of malleability.
5000kg of nitrogen are converted to ammonia in an industrial process. If the conversion is 70% efficient, calculate the expected yield(mass) of ammonia.
M(N) = 14 g/mol M(H) = 1g/mol (Show all working out)
n(N)= m/M, change 5000kg into g which is 5,000,000g, n(N)=5,000,000/14=357142.857 mol
n(NH3)=357142.857 x 0.70 = 250000 mol
M(NH3)= 43g/mol, m(NH3)= n x M, 250000 x 43 = 10,750,000g or 10750kg.
Explain how the surface area of reactants can affect the rate of a chemical reaction. You can use a simple illustration to your answer.
the larger the surface area of reactants the faster the rate of reaction this is shows by powdering of Koko Samoa dissolves faster than the lump of koko samoa.
Discuss the significance of the various processes of the esterification process in real life.
Cosmetics and Perfumes: Ester compounds are extensively used in the production of cosmetics, perfumes, and personal care products. They contribute to the scent, texture, and stability of these products. Esters with different properties, such as volatility and hydrophobicity, are carefully selected to achieve specific fragrance profiles and product characteristics.
Explain how the hardness of water affects its quality and use.
The high amount of Ca and Mg ions makes water lathers really hard thus produces scums which affects the quality and use of water.
Explain why silica (sand) has a high melting point in terms of structure and bonding.
Silica has a similar structure to that of a diamond. It is arranged tetrahedrally where one carbon is bonded to other 4 carbons and the presence of strong covalent bonds the holds the atoms requires more energy to break it thus why it has a high melting point.
Magnesium reacts with hydrochloric acid as shown. Use the equation below to answer questions (i) and (ii). Mg(s) + 2HCl(aq) gives MgCl2(aq) + H2(g) M(Mg) = 24 g/mol M(Cl) = 35.5 g/mol M(H) = 1 g/mol
How many moles of Mg react with 1 mole of HCl?
How many moles of Mg must be reacted to produce 1 mole of H2?
1/2 mole of Mg to react with 1 mole of HCl
1 mole of Mg
The strength of acids and bases depend on their ability to dissociate in aqueous solution. How do you explain that HCl is a strong acid while ethanoic acid is considered a weak acid?
HCl dissociates or ionized completely in water whereas ethanoic acid partially dissociates in water.
HCl + H2O .......... H3O+ + Cl-
CH3COOH + H2O ....... H3O+ + CH3COO-
Draw the structural formulae of 3,4 – dimethylpentan-2-ol
on the board
Explain the effect of green house gases on the climate.
Green house gases such as CO2 affects the climate if it is too much at the atmosphere. The increasing concentration of CO2 on the atmosphere causes too much heat on the planet results in global warming.
Describe the melting point of sodium chloride (NaCl) in terms of bonding between the atoms.
Strong electrostatic forces
Positive ions and negative ions attracted
Ionic bonding forms lattice, conducts electricity or heat in molten state due to mobile electrons.