Which of the following reactions are exothermic?

 

$$\begin{gathered} 1) C + O2 → CO2 \\ 2) 2Mg + O2 → 2MgO \\ 3) CuSO4 + 5H2O → CuSO4.5H2O \\ 4) All the above \end{gathered}$$

The order of basicity in ammonia is different in gaseous phases vs. aqueous phases due to hydrogen bonding.

So in gaseous phases it's the well known: 3' > 2' > 1'> NH3. Just so we're on the same page, this is due to the inductive effect of electron donating alkyl groups--they destabilize the lone pair on nitrogen atom, making nitrogen more basic.

But in aqueous phase, the order is slightly different: 2'> 1'> 3' > NH3.

Allotropes are different structural modifications of an element, that is, each of two or more different physical forms in which an element can exist.

Carbon is capable of forming many allotropes due to its valency. Well-known forms of carbon include charcoal, diamond, graphite, buckminsterfullerene and graphene.

Hence, Ethylene is not an allotrope of Carbon.

3 – Hexanol:

There is no alcohol stretch present in the spectrum. Therefore, the above structure is not suitable for the given spectrum.

Trans – 4 – octene:

There is no vinyl bending present in the spectrum. Therefore, the above structure is not suitable for the given spectrum.

1, 5 – hexadiene:

The vinyl bending and other stretches were matched with the above structure.

Hence, the c = c stretch, vinyl bending and stretch were matched with the above structure.

Therefore, the given spectrum belongs to 1, 5 – hexadiene.

   1) SO2                  2) CH2Cl2                3) PCl3

How to check the given molecules are polar or non polar :

If the electronegativity of the two bonded atoms are different then the bond is polar. Although, some molecules contain polar bonds, the molecule may be non-polar. If the polarity of all the bonds present in the molecule are cancel each other then molecule is non-polar.

In the given options,

SO2  is polar because the dipole moments on the O do not cancel.

PCl3  is polar because the P-Cl bonds do not cancel out.

CH2Cl2  polar because the C-Cl bonds do not cancel.

Hence, in brief, Polar molecules are molecules with net dipole due to the presence of partial positive and partial negative charge.

For example, water is a polar molecule that has partial positive and partial negative charge on it. CO2 is a non polar compound.

Therefore, all the given options SO2, CH2Cl2 and PCl3 are Polar molecules.

Normal Gas welding use oxygen-acetylene.

Depending on what materials you are welding, there are some more options that might be used.

For example - MIG/TIG use Argon, MAG use an argon-something mix.

Covalent type of bonding joins The two hydrogen atoms are joned by Covalent type of bonding.

In this type of bonding, electrons are shared between the atoms in order to fill there valence shells. Thus sharing of electrons take place in between the hydrogen atoms.

The number of protons is equal to the number of electrons. That is the number of positive charges is equal to the number of negative charges.

An electrically charged atom or group of atoms formed by the loss or gain of one or more electrons is called an Ion.

Cation:

An ion is a cation (positive ion) if it is created by electron loss and is attracted to the cathode in electrolysis.

Anion:

An ion is an anion (negative ion) if it is created by an electron gain and is attracted to the anode.

The valence of an ion is equal to the number of electrons lost or gained and is indicated by a plus sign for cations and a minus sign for anions.

Ex: Na +, Cl−, Ca ++,...