Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.
When a salt is added to its saturated solution, the salt
dissolves and the solution becomes super saturated
dissolves and the solution becomes unsaturated
precipitates and the solution remains unchanged
dissolves and crystals are formed
Correct answer is C
The point of saturation is the point it gets to and from thence, the solution can no longer take in the salt anymore. From this point, it begins to form precipitate while the solution remains unchanged.
At what temperature does the solubility of KNO3 equal that of NaNO3?
0°C
20°C
30°C
40°C
Correct answer is B
From the graph, check for their point of intersection and trace it down to the temperature axis.
Pure water can be made to boil at a temperature lower than 100°C by
reducing its quantity
decreasing the external pressure
distilling it
increasing the external pressure
Correct answer is B
The easiest and most drastic way to change the boiling point is by tampering with the pressure above your water. To lower the boiling point, you need simply to decrease its external pressure.
What is the mass of solute in 500cm3 of 0.005moldm−3 H2SO4? ( H = 1, S = 32.0, O=16.0)
0.490g
0.049g
0.245g
0.0245g
Correct answer is C
Using
n = cv where n = no of mole, c = molar concentration(mol/dm3) and v = volume( dm3)
volume = 500cm3 = 0.5dm3, c = 0.005moldm−3
number of mole(n) = c x v = 0.5 X 0.005 = 0.0025mol.
but n = massmolarmass = 0.0025 = mass98 (where 98g/mol is the molar mass of H2SO4)
mass of H2SO4 = 0.0025 x 98 = 0.245g.
a decrease in pressure
an increase in pressure
a decrease in temperature
an introduction of a positive catalyst
Correct answer is A
The equilibrium position is shifted to the left with a decrease in pressure in this system because the number of gaseous molecules on the right is less. (Le-Chatelier's principle).