Answer:
CaCO3
Explanation:
The molecule is formed by the calcium cation Ca+2 and the carbonate anion CO3−2.
Answer:
SAMPLE A - pure substance.
SAMPLE B - homogeneous mixture.
SAMPLE C - heterogeneous mixture.
Explanation:
I need a little more context but I believe you are correct
Answer: 
Explanation: 1 gram is equal to 1000 Milligrams so

Since you go straight across its just multiplication so 0.00200x1000=200mg
To answer it in scientific notation it should just be
mg