Chemistry Questions

The sum of the oxidation numbers in a compound must equal zero. In the compound hydrogen sulfide, H2S, the two hydrogen atoms have an oxidation number of +1, for a total of +2.

Therefore, the oxidation number of sulfur in the compound is -2, and the sum of the oxidation numbers is 0.

An amorphous or non-crystalline solid is a solid that lacks the long-range order that is characteristic of a crystal. In Brief, An amorphous solid is any noncrystalline solid in which the atoms and molecules are not organized in a definite lattice pattern. Such solids include glass, plastic, and gel.

Quartz glass (SiO2) is an amorphous solid due to its short range order of constituent particles. Note Quartz is a crystalline solid while quartz glass is an amorphous solid.

Hardness can be removed by adding sodium carbonate (washing soda) or by passing the water through an ion-exchange column.

Hardness in water is caused by dissolved magnesium ions and calcium ions. These can get into the water when it comes into contact with limestone and other rocks that contain calcium compounds. This can happen, for example, when rainwater flows over these rocks on its way to a reservoir.

Hardness in water is of two types. They are :

1. Temporary hardness

2. Permanent hardness

1. Temporary hardness:: Temporary hardness is caused by dissolved calcium hydrogen carbonate.

2. Permanent hardness:: Permanent hardness is caused by dissolved calcium sulfate. Unlike temporary hardness, it is not removed by boiling the water.

The most common gas people breathe from clean air is nitrogen. Air is a mixture of gases, and the air on Earth contains about 78 percent nitrogen and about 21 percent oxygen. Argon, carbon dioxide neon, helium, methane, krypton, hydrogen and xenon are in much smaller amounts.