The average female voice emits a sound with a wavelength of 0.85 m. Given the speed of sound in air at 340 m/s, what is the frequency:

The frecuency is 400 Hz.

Explanation:

In a periodic wave the wavelength is the physical distance between two points from which the wave repeats itself. It is named by (λ). That is, the wavelength is the minimum distance between two points on the wave that are in the same state of vibration.

Frequency is represented by the letter f, and is the number of vibrations that occur in a unit of time. That is, how many ridges or valleys are repeated in a unit of time.

The propagation speed is the speed with which the wave propagates in the medium, that is, it is the magnitude that measures the speed at which the wave's disturbance propagates along its displacement. Relate the wavelength (λ) and the frequency (f) inversely proportional using the following equation: v = f * λ.

In this case:

Replacing:

340 m/s= f* 0.85 m

Solving:

f= 400 Hz

The frecuency is 400 Hz.

c is the answer because when something is left after something evaporates that shows the chemical change.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.