Environmental Chemistry: Water Quiz

Explanation
Sea water is a mixture of various salts, with sodium chloride being the most abundant. The percentage of sodium chloride in sea water is approximately 3.4%. This means that for every 100 parts of sea water, 3.4 parts are sodium chloride.

Explanation
The density of water is maximum at 4oC because as water cools below 4oC, the hydrogen bonds between water molecules start to form a crystalline structure, causing the molecules to move further apart and decreasing the density. Similarly, as water heats up above 4oC, the hydrogen bonds weaken, causing the molecules to move closer together and also decreasing the density. Therefore, at 4oC, the water molecules are packed together most efficiently, resulting in the highest density.

Explanation
Sodium chloride does not cause water to become hard because it does not contain any calcium or magnesium ions. Hard water is caused by the presence of calcium and magnesium ions, which react with soap to form insoluble scum and reduce its effectiveness. Sodium chloride, commonly known as table salt, only contains sodium and chloride ions, which do not contribute to water hardness.

Explanation
Magnesium hydrogen carbonate is the salt that causes temporary hardness in water. Temporary hardness is caused by the presence of dissolved bicarbonate ions, which can be removed by boiling the water or adding lime. Magnesium hydrogen carbonate is a compound that contains both magnesium and bicarbonate ions, making it the correct answer for causing temporary hardness in water.

Explanation
Heating calcium hydrogen carbonate (Ca(HCO3)2) causes it to decompose, resulting in the formation of calcium carbonate (CaCO3), carbon dioxide (CO2), and water (H2O). In simpler terms, heating calcium hydrogen carbonate causes it to break down into calcium carbonate, carbon dioxide, and water. This type of reaction is often referred to as thermal decomposition.

Explanation
Anemia is not a waterborne disease because it is a condition that occurs when there is a deficiency in the number or quality of red blood cells in the body. It is typically caused by factors such as iron deficiency, vitamin deficiencies, or chronic diseases. Unlike the other options listed, anemia is not caused by ingesting contaminated water or by coming into contact with waterborne pathogens.

Explanation
All of the mentioned options contribute to the contamination of water bodies. Livestock waste contains harmful bacteria and chemicals that can seep into the water and pollute it. Pesticides used in agriculture can be washed away by rain or irrigation and enter rivers, lakes, and groundwater, causing water pollution. Septic tanks, if not properly maintained or located, can leak sewage into the surrounding soil and contaminate nearby water sources. Therefore, all of these activities are responsible for water body contamination.

Explanation
Washing soda is used to remove permanent hardness in water. Permanent hardness is caused by the presence of calcium and magnesium ions in water, which cannot be removed by boiling alone. Washing soda, also known as sodium carbonate, reacts with the calcium and magnesium ions to form insoluble precipitates, which can then be removed through filtration. Therefore, washing soda is an effective solution for removing permanent hardness in water.

Explanation
The correct answer is the Ocean. The ocean is the largest body of salt water on Earth and it contains about 97% of the Earth's water. It covers approximately 71% of the Earth's surface and plays a crucial role in regulating the Earth's climate and supporting various ecosystems.

Explanation
When too many nitrates enter the water, it leads to a process called eutrophication. Eutrophication occurs when there is an excess of nutrients, such as nitrates, in the water. This excessive nutrient load promotes the rapid growth of algae and other aquatic plants. As these plants die and decompose, the oxygen in the water is depleted, leading to a decrease in the overall water quality. This can have detrimental effects on aquatic life, as well as the ecosystem as a whole.