Which of the following reactions are exothermic?

 

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

When two or more chemical species combine to form a single product, the reaction is said to be synthesis reaction. It is also called as Direct Combination reaction.

Here in the given options, Sodium (Na) combines with Chlorine (Cl) to form a more complex single product Sodium Chloride (NaCl).

The chemical element gold has an atomic number 79 is present in period 6 and group 11 of the periodic table.

The process of conversion of sugar to alcohol is called Fermentation in which sugar is coverted to alcohol with the help of yeast.

Ionic character depends on the electronegativity difference between the bonding elements. The greatest the elctronegativity diffference the greatest the ionic character.

Here in the given options, H-F has has the greatest ionic character. The electronegativity of Hydrogen is 2.1 and that of Fluorine is 4. Now the electronegativity difference is 4 - 2.1 = 1.9.

The temperature at which a substance can exist in equilibrium in the liquid, solid, and gaseous states. The triple point of pure water is at 0.01°C (273.16K, 32.01°F).

A substance that dissociates into ions in solution and acquires the capacity to conduct electricity. Sodium, potassium, chloride, calcium, and phosphate are examples of electrolytes, informally known as lytes.