Answer:
The oxidation number of oxygen is -2 and hydrogen is +1
Hope this helps ^-^
Explanation:
<span>A) high to low pressure </span>
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 
Answer: (3) Energy is absorbed as bonds are broken, and energy is released as bonds are formed.
Explanation:
1) The equation given is H₂(g) + Cl₂(g) → 2HCl(g) + energy
2) The energy is shown in the product side, so energy is a product of the reaction, so energy is release.
But this is just the net energy of the process. You need more insight to deal with the energy changes in the reaction.
3) Chemical bonds store energy; this stored energy is the potential chemical energy of the molecules.
When a chemical reaction occurs, the first stage is to brake bonds.
Braking chemical bonds requires energy to overcome the bond energy. Braking bonds always absorbs energy.
On the other hand, forming bonds always release energy.
The neat energy of the reaction is the difference between the energy needed to break bonds and the energy released when new bonds form.
So, regardless the fact that, in the chemical equation that represents the reaction a net energy release is shown, you know that energy is absorbed as bonds are broken, and energy is released as bonds are formed (option 3).