These are chemistry questions and answers categorized according to topics, papers i.e. Paper 1 and 2, Levels i.e. form 1 to form 4, kcse year the examination was done and section A or B
Select topic/category to open topical questions from that particular option provided.
The Fascinating World of Allotropes: Exploring the Different Forms of Elements
An allotrope refers to different forms or structural arrangements of an element that exist in the same physical state but have distinct properties. These variations arise due to differences in the bonding arrangement or the way atoms are arranged within the substance. Allotropes can exhibit different physical and chemical properties, such as color, density, hardness, and reactivity.
One well-known example of allotropes is carbon. Carbon can exist in several allotropes, including diamond, graphite, and fullerenes. Diamond, with its rigid lattice structure, is the hardest naturally occurring substance and is transparent. Graphite, on the other hand, has a layered structure, making it soft and suitable for use as a lubricant or in pencil leads. Fullerenes, such as buckminsterfullerene (C60), have a unique spherical shape and are used in various applications, including in nanotechnology.
Another example is oxygen, which can exist as dioxygen (O2) and ozone (O3). Dioxygen is a colorless, odorless gas that is essential for supporting life through respiration. Ozone, on the other hand, is a pale blue gas that has a distinct smell and plays a crucial role in the Earth's ozone layer, protecting us from harmful ultraviolet radiation.
Allotropes can also exist for other elements, such as sulfur, phosphorus, and selenium, among others. Each allotrope of these elements has different properties and uses. For instance, sulfur can exist as rhombic sulfur, which is yellow and brittle, or as monoclinic sulfur, which is reddish-brown and more stable.
The study of allotropes is important in various scientific fields, including materials science and chemistry. Understanding the different forms of elements and their properties can lead to the development of new materials, technologies, and applications.
In conclusion, an allotrope refers to different forms or structural arrangements of an element that exist in the same physical state but have distinct properties. Allotropes can exhibit different physical and chemical characteristics and play a significant role in various scientific applications and industries.
When 3.18g of cuo were heated carefully in a steam of dry hydrogen,2.54g of Cu and 0.72g of H2O were formed.
(any three 3mks)
b) Study the figure below and answer the questions that follow
Identify the radiations A, B and C (3mks)
- A-Gamma rays
- B-Beta rays
- C-Alpha rays
RCOO – Na+ and RCH2OSO3 – Na+ represent two types of cleansing agents
a) Name the class of cleansing agent to which each belongs (1mk)
b) Which one of the two cleansing agents is likely to pollute the environment. Explain. (2mks)
Because it contain long chains of alkylbenzene and sulphanate which is difficult to be broken by bacteria action
Give a reason why ethanoic acid has a higher boiling point than ethanol which has the same number of Carbon atoms
a) Give a reason why ethanoic acid has a higher boiling point than ethanol which has the same number of Carbon atoms (1mk)
b) Draw the structural formula of ethanoic acid (1mk)
a) Name one chief ore of copper and give its formula (2mks)
Copper pyrites -CuFeS2 (any one 1mk)
Cuprite – Cu2O2
Calculate the mass of copper that would be deposited on the cathode when a steady current of one ampere flows for 20 minutes through copper (II) sulphate solution (Cu = 63.5; Faraday Constance = 96500Cmol-1) (3mks)
The cell convention for an electrochemical cell is shown below
a) Name two substances that can be used as electrolytes in the above cell (2mks)
b) Which of the electrodes is the anode? (2mks)
Define oxidation and reduction in terms of electrons
Calculate the oxidation number of Chromium in Cr2O2- (1mk)
- Waste soap
- Form coating in kettles; Pipes and boilers
- Bursting of hot pipes
a) The solubility of the salt (2mks)
b) The percentage of the salt in the saturated solution (1mk)
Write the equations for the reaction at; (3mks)
Study the experiment below and answer the questions that follow. The gas produced ignites spontaneously
i) Which metal is used above (1mk)
ii) Which gas was produced (1mk)
iii) What will be the colour of phenolphthalein indicator in the resulting solution? (1mk)
Name one gas used together with oxygen in welding other than acetylene gas (1mk)
State two other uses of the gas named above (2mks)
- Used in balloons
- Used in the manufacture of ammonia gas
- Used in the manufacturer of hydrochloric acid
The result is shown below;
i) Which ink was contaminated with substance P (1mk)
ii) Name the ink which was pure (1mk)
iii) Identify the other ink which was not pure (1mk)
Acid Bases And Indicators
Acids Bases And Salts
Air And Combustion
Carbon And Its Compounds
Chemistry Practical Assignments
Chlorine And Its Compounds
Definition Of Chemistry Terms
Differences In Chemistry
Electric Current On Substance
Electrochemistry I And II
Energy Changes In Chemical And Physical Processes
Form 1 Level
Introduction To Chemistry
Nitrogen And Its Compounds
Organic Chemistry I
Organic Chemistry II
Reaction Rates And Reversible Reactions
Simple Classification Of Substances
Structure Of The Atom And The Periodic Table
Structures And Bonding
Sulphur And Its Compounds
Water And Hydrogen
Maurice Atika is a teacher and a netprenuer.