I may be totally wrong but I’ll make a guess to it being thermodynamics.
<span>2 phosphorus and 5 oxygen</span>
Answer:
The balanced half-reaction for the reduction of dichromate ion to chromium ion in acidic aqueous solution:

Explanation:
The reaction :

Balancing of reaction in an acidic medium:
Step 1: Balance the atoms in the reaction:

Step 2: Balance oxygen atom by adding water on the side where no oxygen or less oxygen atom is present;

Step 3: Balance the hydrogen atom by adding hydrogen ions on the side where water is absent:

Step 4: Now balance charge by adding electrons on the side where more positive charge is present

The balanced half-reaction for the reduction of dichromate ion to chromium ion in acidic aqueous solution:

1.94 * 6. 01 = 11.7 which is approximately same as 11 700. So the answer is 3).
Answer:

Explanation:
The frequency and the wavelength of a wave are related by the equation

where
v is the speed
f is the frequency
is the wavelength
For the sound wave in this problem, we have
f = 634 Hz (frequency)
(wavelength)
Therefore, the speed of the wave is

The speed of sound in air depends on the temperature according to the equation

where T is the temperature.
In this problem, we know the speed, so we can calculate the temperature: