Answer:
C
Explanation:
Electromagnetic waves travel at the speed of light and do not require molecules (gas, solid or liquid) to vibrate and travel.
Soundwaves when singing or from thunder vibrate particles to reach our ears and are known as mechanical waves.
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Answer: There are
atoms of hydrogen are present in 40g of urea,
.
Explanation:
Given: Mass of urea = 40 g
Number of moles is the mass of substance divided by its molar mass.
First, moles of urea (molar mass = 60 g/mol) are calculated as follows.

According to the mole concept, 1 mole of every substance contains
atoms.
So, the number of atoms present in 0.67 moles are as follows.

In a molecule of urea there are 4 hydrogen atoms. Hence, number of hydrogen atoms present in 40 g of urea is as follows.

Thus, we can conclude that there are
atoms of hydrogen are present in 40g of urea,
.
Answer:
The ratio of acid to conjugate base is outside the buffer range of 10:1.
Explanation:
The Henderson-Hasselbalch equation for a buffer is
![\text{pH} = \text{pK}_{\text{a}} + \log\dfrac{\text{[A$^{-}$]}}{\text{[HA]}}](https://tex.z-dn.net/?f=%5Ctext%7BpH%7D%20%3D%20%5Ctext%7BpK%7D_%7B%5Ctext%7Ba%7D%7D%20%2B%20%5Clog%5Cdfrac%7B%5Ctext%7B%5BA%24%5E%7B-%7D%24%5D%7D%7D%7B%5Ctext%7B%5BHA%5D%7D%7D)
A buffer should have
![\dfrac{1}{10} \leq \dfrac{\text{[A$^{-}]$}}{\text{[HA]}} \leq \dfrac{10}{1}](https://tex.z-dn.net/?f=%5Cdfrac%7B1%7D%7B10%7D%20%5Cleq%20%5Cdfrac%7B%5Ctext%7B%5BA%24%5E%7B-%7D%5D%24%7D%7D%7B%5Ctext%7B%5BHA%5D%7D%7D%20%5Cleq%20%5Cdfrac%7B10%7D%7B1%7D)
For a solution that is 1.3 mol·L⁻¹ in HF and 1.3 mmol·L⁻¹ in KF, the ratio is

The ratio of acid to conjugate base is 1000:1, which is outside the range of 10:1.
A is wrong. NF is a weak acid.
C is wrong. The two species are a conjugate acid-base pair.
D is wrong. Salts of Group 1 metals are soluble.
The force acting between two charged particles A and B is 5.2 x 105 newtons. Charges A and B are 2.4 x 102 meters apart. If the charge on particle A is 7.2 x 108 coulombs, what is the charge of particle B? (k 7 9.0 x 109 newton meters?/coulomb)