Which of the following statements about electromagnetic and mechanical waves is true?

A. Electromagnetic waves must travel through a medium, but mechanical waves do not require a medium.

B. Mechanical waves must travel through a medium, but electromagnetic waves do not require a medium.

C. Mechanical waves sometimes travel through a vacuum, and electromagnetic waves sometimes travel through matter.

D. Electromagnetic waves travel mostly through matter, and mechanical waves travel mostly through a vacuum.

B. Mechanical waves must travel through a medium, but electromagnetic waves do not require a medium.

Explanation:

A wave is defined as any disturbance that transmits energy from one point to another.

Waves can be typically classified as either mechanical or electromagnetic waves.

Mechanical waves are waves that requires a medium for their propagation. In a vacuum, they cannot be propagated and would not cause any disturbance. An example is sound waves.

Electromagnetic waves do not require a medium to be propagated. They can pass through any substance in nature. Electromagnetic radiations belongs to this class.

The solution for this problem would be:
H + ions from pH = 4.0 x 10^-4 moles.
But H2SO4 gives off 2 moles of H+ ions / mole.
Moles of H2SO4 = 2.0 x 10^-4
Mass = 2 x 10^-4 moles x 98 = 1.96 x 10^-3 grams
1.96 x 10^-3 grams / 10^3 = 1.96 x 10^-6 Kg.