Answer: 17) d. 
18. c. The empirical formula of a compound can be twice the molecular formula.
Explanation:
Molecular formula is the chemical formula which depicts the actual number of atoms of each element present in the compound.
Empirical formula is the simplest chemical formula which depicts the whole number of atoms of each element present in the compound.
To calculate the molecular formula, we need to find the valency which is multiplied by each element to get the molecular formula.
The equation used to calculate the valency is:

The empirical mass can be calculated from empirical formula and molar mass must be known.
17. Thus the empirical formula of
should be 
18. The molecular formula will either be same as empirical formula or is a whole number multiple of empirical formula. Thus the empirical formula of a compound can never be twice the molecular formula.
A.) 1.
b.) 3
c.) 2
I hope this helps.
The 28 is the sum of the protons and neutrons in the element silicon.
ALL silicon atoms have 14 protons in the nucleus, so we can turn this into an equation:
#protons + #neutrons = 28
14 + #neutrons = 28
#neutrons = 14
#protons = 14
Explanation:
Since pressure remained constant, we can eliminate P from the equation

Doing some algebra and converting temperature to Kevin by adding 273, you should obtain the same result.
Answer:
8. A boat, cars, airplanes
9. It's safer to practice techniques on life sized models of human organs than practicing on an actual human. If you mess up on a model it doesn't matter, messing up on a human can put their life at risk.