17. which of the following is not an empirical formula? *

a. sb2s3

b. c2h3o

c. beso4

d. c2h6

18. which of the following is not true comparing empirical and molecular formulas? *

a. the molecular formula can be a simple whole number multiple of the empirical formula.

b. the molecular formula of a compound can identical to its empirical formula.

c. the empirical formula of a compound can be twice the molecular formula.

d. several compounds can start with the same empirical formula, but have different molecular formulas.

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.

(newtons first law)

conservation of momentum law states :

momentum before collision = momentum after collision

momentum p (kg-m/s)= mass * velocity

say moving car=1 000 kg, velocity = 10 m/s then p = 1 000*10= 10 000 kg-m/s

say still car = 2 000 kg, velocity = 0 m/s then p = 2 000* 0 = 0 kg-m/s

total momentum prior to collision = 10 000 + 0 = 10 000 kg-m/s

momentum after collision = 10 000 kg-m/s

mass now = 1 000 kg+2 000 kg = 3 000 kg

10 000 = 3 000 kg* velocity m/s

10 000/3 000 = velocity

3.33 m/s = velocity after collision

an impulse is a force applied over time , momentum is exclusive of external forces and a perfect collision is implied