Explanation:
1.
Given parameters:
Frequency of the radiation = 8.4 x 10¹⁴Hz
Unknown:
Energy of the wave = ?
Solution:
The energy of a wave is given by the expression below;
E = hf
E is the energy
h is the Planck's constant = 6.63 x 10⁻³⁴m²kg/s
f is the frequency
Now insert the parameters and solve;
E = 6.63 x 10⁻³⁴m²kg/s x 8.4 x 10¹⁴Hz
E = 5.57 x 10¹ x 10⁻²⁰J
E = 5.57 x 10⁻¹⁹J
2.
Given parameters:
Wavelength = 2.13 x 10⁻¹³m
Unknown:
Frequency of the wave = ?
Solution:
The frequency of a wave can be determined using the expression;
C = f∧
C is the speed of light = 3 x 10⁸m/s
f is the frequency
∧ is the wavelength
f = 
= 
= 1.41 x 10²¹hz
Answer: 1. C. polar covalent: electrons shared between silicon and sulfur but attracted more to the sulfur
2. B) 
3. B) Fluorine
Explanation:
1. A polar covalent bond is defined as the bond which is formed when there is a difference of electronegativities between the atoms.
Electronegativity difference = electronegativity of sulphur- electronegativity of silicon = 2.5 -1.8 = 0.7
Thus as electronegativity difference is less than 1.7 , the cond is polar covalent and as electronegativity of sulphur is more , the electrons will be more towards sulphur.
2. A molecular compound is usually composed of two or more nonmetal elements. Example:
Ionic compound is formed by the transfer of electrons from metals to non metals. Example: 
, 
and 
3. For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Here K is having an oxidation state of +1 and as the compound formed is KZ, the oxidation state of non metallic element Z should be -1. Thus the element Z is flourine which exists as diatomic gas 
The chemical reaction of Cavendish involving zinc would be a reaction between hydrochloric acid and zinc yielding zinc chloride and hydrogen gas. The balanced chemical equation would be:
2Zn + 2HCl = 2ZnCl + H2
This is an example of a single replacement reaction where zinc replaces hydrogen in the acid molecule.
1Al2(SO4)3 + 3ZnCl2 → 2AlCl3 + 3ZnSO4
The coefficients represents moles. There is 1 mole of Aluminum Sulfate, 3 moles of Zinc(II) Chloride, 2 moles of Aluminum Chloride, and 3 moles of Zinc(II) Sulfate.
Now add all the coefficients/moles.
9 is the sum of all the coefficients.
