What is the mass number of an element having 20 neutrons, 15 protons and 15 electrons?
15
30
35
50
Correct answer is C
Mass number = Protons = Neutrons = 15 + 20 = 35
The electronic configuration of an element X is 1s22s 22s63p 2 3p4. It can be deduced that X
Belongs to group 6 of the Periodic Table
Belongs to group IV of the Periodic Table
has 3 unpaired electrons in its atom
has relative molecular mass of 16
Correct answer is A
No explanation has been provided for this answer.
Which of the following measures is not suitable for controlling water pollution?
treating industrial effluent and domestic sewage before discharge into water
Controlling the use of agrochemicals
recycling industrial and agricultural wastes
burning industrial and agricultural wastes before discharge into water ways
Correct answer is D
No explanation has been provided for this answer.
lower the temperature
increase the concentration
facilitate the precipitation of solid
reduce the viscosity of the solution
Correct answer is C
No explanation has been provided for this answer.