Answer:
OPTION (A) : Testing a rock sample for gold content
Explanation:
For testing a rock sample of gold content you will need a Chemist. To test the material, the sample is rubbed on black stone which will leave a mark on the stone. This mark is tested by applying aqua fortis i.e nitric acid on the mark. If the mark gets dissolve then the material is not gold. If the mark sustain the it is further tested by applying aqua regia i.e nitric acid and hydrochloric acid which will prove the sample is of gold if it gets dissolve on using hydrochloric acid. The purity of the sample can be checked by differing the concentration of the aqua regia and comparing it with the gold material of the known purity.
True!
Energy released by system is absorbed by surroundings.
Answer: 1. Alcohol 2. Ester
Explanation:
Right on edge.
Answer:
have stars that might appear to wobble
often have one star that is brighter than the other
Explanation:
A binary star system is a star system made up of mostly two stars that moves round their common fixed center.
The two orbiting stars are gravitationally bonded to one another and they move round each other.
Most binary stars might appear wobble. One of the stars often appears brighter than the other.
A pure substance that cannot be separated into simpler substances by physical or chemical means. A pure substance composed of two or more elements that are chemically combined.
