Answer:

Explanation:
Calcium is the element of the group 2 and period 4 which means that the valence electronic configuration is
.
Chlorine is the element of the group 17 and period 3 which means that the valence electronic configuration is
.
Thus, calcium losses 2 electrons to 2 atoms of chlorine and these 2 atoms of chlorine accepts each electron to form ionic bond. This is done in order that the octet of the atoms are complete and they become stable.
Ca Cl
2 1
Cross multiplying the valency, We get, 
Thus, the formula of calcium chloride is
.
Explanation:
The observable visible spectrum of Cr(acac)3 complex is different from that of
[Cr(en)3]Br3 due to strength of bonded ligand in the coordination sphere.
en is a strong field ligand compared to acac thus pairing occurs. In both the complexes
Cr is in +3 state, configuration [Ar] 3d^3. There are 3 unpaired e in Cr(acac)3 whereas 1 unpaired e in [Cr(en)3]Br3 due to pairing.
A beaker of black powder can be a mixture with different substances (i.e gunpowder: a mixture of sulfur, charcoal, etc.), an element which can probably be carbon (known as black), and a compound as well which can be potassium nitrate. Hence, the answer is D.
Na22 and Na24 are isotopes
Answer:
0.1 mol
Explanation:
Number of mole= mass/molar mass
lithium have a mass number of 7 and oxygen have a mass number of 16.
so, (7x2) + 16
= 30
therefore, number of moles = 2.93/30
= 0.10