The question is incomplete, the complete question is;
Which statement describes a difference between electromagnetic and mechanical waves?
A. Mechanical waves cannot be longitudinal, but electromagnetic waves can.
B. Electromagnetic waves cannot move particles, but mechanical waves can.
C. Electromagnetic waves do not require a medium, but mechanical waves do.
D. Mechanical waves do not transfer energy, but electromagnetic waves do.
Answer:
Electromagnetic waves do not require a medium, but mechanical waves do.
Explanation:
A wave is defined as a disturbance along a medium which transfers energy. Waves may be classified as mechanical waves or electromagnetic waves based on their medium of propagation.
A mechanical wave requires a material medium for propagation. An example of a mechanical wave is sound waves. Sound waves are propagated in air.
Electromagnetic waves do not require a material medium for propagation. They can travel through space. An example of electromagnetic waves is light waves.
Answer:
(C) knowing which minerals are in a rock can help you identify and classify that rock.
Explanation:
It is the truth.
Explanation:
Formation of formate buffer will be as follows.
Formate buffer = HCOOH + HCOONa
Molar mass of HCOOH 
= 46 g/mol
Molar mass of HCOONa 
= 68 g/mol
of HCOOH = 3.75
As, ![[HCOO^{-}]](https://tex.z-dn.net/?f=%5BHCOO%5E%7B-%7D%5D)
= [HCOOH] + [HCOONa]
= [HCOONa] (here, dissociation of HCOOH is negligible)
Its preparation will be as follows.
750 ml of 0.25 M sodium formate buffer
Since, there are many combinations of salt + acid and among those possibilities one of them is as follows.
HCOONa = 0.25 M in 400 ml solution
HCOOH = x molat in 350 ml solution
Therefore as, pH = 
4 = 3.75 + 
x = 0.16 M
Therefore, molarity of the formic acid acid is 0.16 M.
Now, calculate the weight of sodium formate as follows.
= 6.8 g
And, number of milliliters of formic acid required is 350 ml.
Bottle of water-could be probably
