Which of the following metals does not react with water to produce hydrogen?
Copper
Potassium
Sodium
Zinc
Correct answer is A
Most alkali metals and alkaline earth metals react with water to produce hydrogen. The alkali metals comprise Group 1 of the periodic table, and include lithium, sodium, potassium, etc.
- Zinc is not much reactive with cold or room temperature water but reacts with steam to form zinc oxide and liberate hydrogen gas.
- Copper lies below hydrogen in the activity series of metals, therefore it can not displace hydrogen from water
"Electrons always occupy the lowest empty energy level" is a statement of
Aufbau Principle
Hund's rule
Pauli Exclusion Principle
Periodic law
Correct answer is A
- The Aufbau principle states that electrons fill lower-energy atomic orbitals before filling higher-energy ones
0.010
0.020
0.100
0.150
Correct answer is B
\(frac{CaVa}{CbVb}\) = \(frac{Na}{Nb}\)
( 0.01 X 20 ) / (Cb X 20) = 1 / 2
cross multiply → Cb = (0.01 X 20 X 2) / ( 20 X 1)
Cb = 0.02 mol/dm\(^3\)
How many moles of H\(_2\)SO4 are there in 50 cm\(^3\) of 0.108 mol dm\(^3\) solution of the acid?
5.4x 10
5.4 x 10\(^{-3}\)
5.4 x 10\(^{-2}\)
5.4x 10\(^{-1}\)
Correct answer is B
No. of moles = \(\frac{molar conc \times volume}{1000}\)
No. of moles = \(\frac{0.108 \times 50}{1000}\)
: No. of moles = 0.0054 moles = \( 5.4 \times 10^{-3}\)
Which of the following statements about the solubility of a salt is correct?
A salt whose solubility increases with temperature would not crystallize easily on cooling
A salt whose solubility is independent of temperature would normally crystallize out on cooling
Crystallization would be efficient in separating out a salt whose solubility increases considerably with temperature
Solubility of a solid does not affect its crystallization
Correct answer is C
Crystallization is based on the principles of solubility: compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound.