2020 - JAMB Chemistry Past Questions and Answers - page 4
The chlorinated alkane often used industrially to remove grease is?
Tetrachloromethane
Chloromethane
Trichloromethane
Dichloromethane
Tetrachloromethane is an effective solvent within the chemical industry and is used to clean machinery and electrical equipment. That is to say that it functions as a solvent for oils, fats, lacquers, varnishes, rubber waxes, and resins, and as a grain fumigant.
What mass of water is produced when 8.0g of hydrogen reacts with excess oxygen?
8.0g
16.0g
36.0g
72.0g
2H\(_2\) + O\(_2\) ⇒ 2H\(_2\)O
From the equation:
4g of Hydrogen produces 36g of water
8g of Hydrogen will produce 72g of water
Proteins in acid solution undergo?
Substitution
Fermentation
Hydrolysis
Polymerisation
Acid hydrolysis refers to a hydrolysis reaction occurring under acidic conditions. Acid hydrolysis of a protein breaks the polymer down into its constituent amino acids.
In organic chemistry, acid hydrolysis is a hydrolysis process in which a protic acid is used to catalyze the cleavage of a chemical bond via a nucleophilic substitution reaction, with the addition of the elements of water. For example, in the conversion of cellulose or starch to glucose. Wikipedia
The general formula for the Alkanals is?
R\(_2\)CO
RCHO
ROH
RCOOR
Alkanals (Aldehydes) have the general formula RCHO while Alkanones or Ketones have the general formula RCOR'.
Where R and R' may be alkyl or aryl groups.
When cathode rays are deflected onto the electrode of an electrometer, the instrument becomes?
Bipolar
Negatively charged
Positively charged
Neutral
When these cathode rays are deflected onto an electrode of an electrometer, the instrument measured a negative charge. The rays tested also were deflected by the application of an electric field.
When a solid substance disappears completely as a gas on heating, the substance is said to have undergone?
Sublimation
Crystallization
Distillation
Evaporation
Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state
An electron can be added to a halogen atom to form a halide ion with?
8 valence electrons
7 valence electrons
2 valence electrons
3 valence electrons
A halide ion is a halogen atom bearing a negative charge. The halide anions are fluoride (F−), chloride (Cl−), bromide (Br−), iodide (I−) and astatide (At−). Such ions are present in all ionic halide salts. Halide minerals contain halides.
More.
Aluminum hydroxide is used in the dyeing industry as a?
Dye
Dispersant
Salt
Mordant
Aluminium hydroxide, Al(OH)₃ is used as a mordant in dyeing.
The most important element on the earth's crust is?
Nitrogen
Hydrogen
Oxygen
Fluorine
Earth's crust is made up of several elements: oxygen, 46.6% by weight; silicon, 27.7%; aluminum, 8.1%; iron, 5%; calcium, 3.6%; sodium, 2.8%, potassium, 2.6%, and magnesium, 2.1%.
To obtain pure carbon(ii)oxide from its mixture with carbon(iv)oxide, the mixture should be?
Passed over heated copper(ii)oxide
Bubbled through water
Bubbled through conc H\(_2\)SO\(_4\)
Bubbled through conc NAOH
Carbon monoxide, that is Carbon(ii)oxide is prepared from carbon(iv)oxide by passing the latter through red-hot carbon and the unchanged CO\(_2\) is removed when the mixture of the gases through conc NAOH.