Question

What are the constituents of ‘Mischmetal’?
A) La, Fe
B) La, Ce
C) Fe, Ce
D) Ce, Cu

Answer 1

It is an alloy and therefore constitutes various elements but the main two are part of lanthanide series. The Lanthanide series is present in the bottom of the periodic table.

Complete answer:
Mischmetal is an alloy of rare earth elements. It is also known as cerium mischmetal or rare earth mischmetal. An approximate composition includes 55% cerium, 25% lanthanum and 15-18% neodymium and praseodymium. It contains 95% lanthanoid and iron 5%. Its most common use is in the lighters and torches.

Therefore, the correct option is B.

Additional Information: Mischmetal is used in the preparation of mostly all rare-earth elements. This is because such elements are nearly identical in most chemical processes meaning that ordinary extraction processes do not distinguish them. Highly specialized processes exploit differences in solubility to separate mischmetal into its constituent elements, with each step producing only an incremental change in composition. Such processes later informed Marie Curie in her search for new elements.
Cerium is a chemical element with the symbol Ce and atomic number 58. It is soft, ductile and silvery white metal that tarnishes when exposed to air and is soft enough to be cut with a knife. It is the second element of the lanthanide series. It has +3 oxidation state and is one of the rare earth elements. It has no biological role in humans and is not toxic.

Note: Having information about alloys can help in knowing about mischmetal. Also knowing about cerium and lanthanum is important. Lanthanum has symbol La and atomic number 57. It also has the same physical properties as that of cerium. It also has +3 oxidation state. It is not toxic to humans.