Which of the following reactions are exothermic?

 

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

Acid Precipitation or Acid rain is caused by a mix of Sulfur Dioxide, Carbon Dioxide, Nitrogen Oxides.

A Chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as Acid Rains.

Polarity :: 

The polarity of a molecule defines its other physical properties such as melting point, boiling point, surface tension, vapor pressure etc... Simply, polarity occurs when the electron distribution in a molecule is asymmetric. This results in a net dipole moment in the molecule. One end of the molecule is charged negative while the other gets a positive charge.

The polarization of a molecule greatly depends on the shape of the molecule. A diatomic molecule like HF mentioned above has no issue of shape. The net dipole moment is only due to the uneven distribution of electrons between the two atoms. However, when there are more than two atoms involved in making a bond, there are many complexities.

The water molecule is of bent shape. Therefore, when the two pair of electrons shared by oxygen with two hydrogen atoms is pulled towards oxygen, the net dipole moment results in the direction of the oxygen atom. There is no other force to cancel out the resultant dipole moment. Hence, the water molecule is highly polar.

Ammonia molecule is of a pyramid shape and the electronegative N atom pulls the electrons towards itself. The three N-H bonds are not in the same plane; hence the dipole moments created do not get canceled out. This makes ammonia a polar molecule.

However, the dipole moments sometimes get canceled due to the shape of the molecules, making the molecule non-polar. Carbon dioxide is such a molecule.

The nucleus of hydrogen consists of only a single proton.

Its parts are a single negatively-charged electron that circles a single positively-charged nucleus of the hydrogen atom.

The electron is bound to the nucleus by the Coulomb force.

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms activities.

Photosynthesis can be represented using a chemical equation.

The overall balanced equation is

              $$\begin{gathered} 6CO2 + 6H2O →Sunlight C6H12O6 + 6O2 \\ Source of Carbon & Oxygen + \\ Source of Electrons & Hydrogen + \\ Energy that drives Photosynthesis ----> \\ Sugar + Gas produced by splitting water. \end{gathered}$$

Where 

CO2 = carbon dioxide 

H2O = water

C6H12O6 = glucose 

O2 = oxygen.

Tetraethyl lead is a highly toxic compound used as a gasoline additive.

Tetraethyl lead abbreviated as TEL, is an organo lead compound with the formula (CH₃CH₂)₄Pb. It is a petro-fuel additive which in turn caused increased vehicle performance. This is also used as an antiknock agent in gasoline and jet fuels. Tetraethyl lead is absorbed rapidly by the skin, the lungs, and the gastrointestinal tract. It is converted to triethyl lead, which might be responsible for its toxicity.

Proteins are long chains of Amino acids. That is in brief, Amino acids are the monomers of Proteins. Amino acids are compounds which contain both an amino group and a carboxylic group. Proteins are made up of 20 essential amino acids.

Monomer means a small molecule of an organic substance i.e, building block in general.

Helium has the highest First Ionization Energy in the Noble Gases group.

Ionization Energy ::

Ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms. Atoms are more stable when they have full valence shells.

Noble Gases have a very stable electron configuration, therefore, they have the highest amount of ionization energy within their periods. It decreases down a family because electrons farther from the nucleus are easier to remove.

Ionization Energy levels of Noble Gases group in Descending Order :: He, Ne, Ar, Kr, Xe, Rn

Given Equation is 

Mg + O2 → MgO

Balancing the Chemical Equation is nothing but Conservation of Matter. As Matter is Neither created nor Destroyed, it must be conserved.

Here we have 1 Mg and 2 O on the left side and 1 Mg and 1 O on the right side

To balance that, add 1 Mg on the left side so that it becomes 2 Mg and 2 O on the left side

i.e,

2 Mg + O2 → 2 MgO

Here it has 2 Mg & 2 O on the left side and 2 Mg and 2 O on the right side and the Chemical equation is Balanced.