Which of these chemical equations demonstrates the law of conservation of mass as it applies to the combustion of ethane? a. 2 c 2 h 6 + 7 o 2 → 4 c o 2 + 6 h 2 o b. c 2 h 6 + 3 o 2 → 2 c o 2 + 3 h 2 o c. c 2 h 6 + 5 o 2 → 2 c o 2 + 3 h 2 o d. 2 c 2 h 6 + 5 o 2 → 4 c o 2 + 4 h 2 o

A.2 C₂ H₆ + 7 O₂ → 4 C O₂ + 6 H₂ O

according to law of conservation of mass , the total mass of reactants side must be same as the total mass of product side. so we need to check if each atom in the equation has same number on both side of the equation or not.

in this equation , we have

4 atoms of carbon left and 4 atoms of carbon on right

12 atoms of hydrogen on left and 12 atoms of hydrogen on right

14 atoms of oxygen on left and 14 atoms of oxygen on right

compass can be used day and night, cloudy or sunny

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.