Chemistry - Study Mode

[#651] Which metal does not undergo corrosion due to the formation of oxide layer?
Correct Answer

(C) Aluminium

Explanation

Solution: Corrosion is an oxidation reaction with atmospheric oxygen in the presence of water on the surface of a metal. Iron corrodes more quickly than most other transition metals to form an iron oxide. Aluminium also undergoes an oxidation reaction, but does not oxidize and corrode as quickly as its reactivity suggests. Once a thin oxide layer of Al2O3 has formed on the surface, it forms a barrier to oxygen and water to prevent further corrosion of the aluminium.

[#652] The wire of flash bulb is made of:
Correct Answer

(C) Magnesium

Explanation

Solution: The first modern photoflash bulb (or flashbulb) was made by Austrian Paul Vierkotter, who used magnesium coated wire in an evacuated glass globe. It was later determined that aluminum foil in a low pressure oxygen atmosphere worked even better, and was cheaper to produce.

[#653] Identify the metal which is non toxic in nature.
Correct Answer

(B) Gold

Explanation

Solution: Toxic metals are metals that form poisonous soluble compounds and have no biological role, i.e. are not essential minerals, or are in the wrong form. Most often the definition includes at least cadmium, lead, mercury and the radioactive metals. Metals in an oxidation state abnormal to the body may also become toxic: chromium (III) is an essential trace element, but chromium(VI) is a carcinogen. Similarly, cobalt could also be toxic.

[#654] Iron rusts quickly in
Correct Answer

(B) Sea water

Explanation

Solution: Water is the enabler of fast oxidation of iron. So freshwater will also cause rust. However, salt water (sea water) is a very good conductor (lots of dissociated ions) and so there are a number of electrolysis reactions that tremendously accelerate corrosion in salt water. This effect can be reversed by using a metal (like zinc) which causes the current to be reversed and in effect the zinc corrodes rapidly, protecting the iron.

[#655] Sour taste of ‘Coca Cola’ is due to the presence of
Correct Answer

(B) Phosphoric acid

Explanation

Solution: Food-grade phosphoric acid (additive E338) is used to acidify foods and beverages such as various colas, but not without controversy regarding its health effects. It provides a tangy or sour taste and, being a mass-produced chemical, is available cheaply and in large quantities. The low cost and bulk availability is unlike more expensive seasonings that give comparable flavors, such as citric acid which is obtainable from citrus, but usually fermented by Aspergillusniger mold from scrap molasses, waste starch hydrolysates and phosphoric acid.