Answer:
About 60.
Explanation:
Mendeleev knew of 63 elements. He wrote their properties on cards and arranged them in order of atomic mass.
That's how he discovered that the properties of elements are periodic functions of their atomic masses.
Answer:
pKa = 4.89.
Explanation:
We can solve this problem by using the <em>Henderson-Hasselbach equation</em>, which states:
pH = pKa + log ![\frac{[A^-]}{[HA]}](https://tex.z-dn.net/?f=%5Cfrac%7B%5BA%5E-%5D%7D%7B%5BHA%5D%7D)
In this case [A⁻] is the concentration of sodium benzoate and [HA] is the concentration of benzoic acid.
We <u>input the given data</u>:
4.63 = pKa + log 
And <u>solve for pKa</u>:
pKa = 4.89
Answer:

Explanation:
1. Calculate the work
w = - pΔV = -4.3 atm × (43 L - 20 L) = -4.3 × 23 L·atm = -98.9 L·atm
2. Convert litre-atmospheres to joules

The negative sign indicates that the work was done against the surroundings.
<span>Stating that collisions of gas particles are perfectly elastic means that no kinetic energy is lost when the gases collide, and no kinetic energy is gained. Some of the properties of gases include volume, pressure, thermal conductivity, pressure, and viscosity.</span>