It is softer than topaz and and it is softer than diamond (diamond has a Mohs hardness of 10, which is the highest value of the scale)
If the half-life of a sample of a radioactive substance is 30 seconds, how much would be left after 60 seconds? <span>
A. one-fourth</span>
Answer:
D
Explanation:
Organic compounds are chemical compounds which usually contains one or more atoms of carbon, hydrogen, oxygen and sometimes nitrogen or sulphur. Carbon and hydrogen are the main element that is contained in most organic compounds.
Option A is wrong because calcium phosphate is not an organic compound, although all the other compounds in the option are organic compounds.
Option B is wrong because calcium chloride is not an organic compound
Option C is wrong also as calcium sulphate is not an organic compound
Option D is correct as all are organic compounds
