Chemistry Questions

The main constituent of biogas is methane (55-70%), CO2 (30-45%) and some traces of gases such as H2S and ammonia.

Biogas is produced under anaerobic conditions; the process is denominated as anaerobic digestion.

The process of conversion of milk into curd is called fermentation.  It is a chemical change. Milk consists of globular proteins called casein. As the microorganism lactobacillus react with milk and turn it to curd. For it 37 degree temperature is needed. But sometimes when it does not get favourable condition, then other microorganism react and makes the curd taste different.

When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.

Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

In a chemical reaction, substances (elements or compounds) called reactants are changed into other substances (compounds or elements) called products. Hence, reactants are those which start the chemical reaction.

For example:

1. In the burning of natural gas, methane (CH4) and oxygen (O2) are the reactants in the chemical reaction. are the substances formed by a chemical reaction. In the burning of natural gas, carbon dioxide (CO2) and water (H2O) are the products formed by the reaction.

2. H2+O2 ----> H2O

Here H2 & O2 are called Reactants and H2O is called Product.

Colored aqueous solutions are a characteristic of transition compounds.

The only transition compound in the above choices is CrCl3.

Cr is a transition element.