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 sodium fusion test, or Lassaigne's test, is used in elemental analysis for the qualitative determination of the presence of foreign elements, namely halogens, nitrogen, and sulphur, in an organic compound. It was developed by J. L. Lassaigne.Silver fluoride is soluble in water and does not precipitate and thus this method cannot be used for detection of fluorine.

HCHO: The carbon and and the oxygen are bonded through a double bond which counts as "one electron pair". Hence the molecule has three electron pairs and is trigonal planar.

The Standard hydrogen electrode (abbreviated SHE), is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials. Its absolute electrode potential is estimated to be 4.44 ± 0.02 V at 25 °C, but to form a basis for comparison with all other electrode reactions, hydrogen's standard electrode potential (E0) is declared to be zero volts only at 298.

Hydrogen has two possible oxidation numbers: +1 and -1.

-1 in case of hydrides.

Potassium bicarbonate (also known as potassium hydrogen carbonate or potassium acid carbonate) is the inorganic compound with the chemical formula KHCO3. It is a white solid

Sodium bicarbonate is a white solid that is crystalline, but often appears as a fine powder.

LiHCO3 is found in solution form while rest alkali metals hydrogen carbonates are solid due to the anomalous properties of Li and its diagonal relationship with the Mg.

Paper production is basically a two-step process in which a fibrous raw material is first converted into pulp, and then the pulp is converted into paper. The harvestedwood is first processed so that the fibres are separated from the unusable fraction of the wood, the lignin. Pulp making can be done mechanically or chemically. In the chemical pulping process, alkali (e.g., sodium hydroxide in the form of a lye or caustic soda) is usually used to remove the lignin that binds the fibres. So, for degumming of raw material, caustic soda is used.