1. all elements are made of small particles called atoms
2. atoms of one element are identical in their properties, different atoms from different elements differ in properties
3. chemical reactions consist of atoms rearranging in whole number ratios
4. atoms can not be subdivided, created, or destroyed
Use Henderson Hasselbache
PH=pka+log([salt]/[acid])
Pka=-log(ka)
-log(1.4x10^-4)= 3.85
log(.83/.14)= .77
3.85+.77= 4.62
PH=4.62
Answer:

Explanation:
We will need a balanced chemical equation with masses, moles, and molar masses.
1. Gather all the information in one place:
Mᵣ: 18.02
2Na + H₂O ⟶ 2NaOH + H₂
m/g: 72.0
2. Moles of H₂O

3. Moles of Na
The molar ratio is 2 mol Na/1 mol H₂O.

Answer:
(B) 3
Explanation:
Citric acid has an acid dissociation constant (Ka) of 8.4 × 10⁻⁴. When it forms a buffer with its conjugate base (citrate), we can calculate the pH using the Henderson-Hasselbalch's equation.
![pH=pKa+log\frac{[base]}{[acid]}](https://tex.z-dn.net/?f=pH%3DpKa%2Blog%5Cfrac%7B%5Bbase%5D%7D%7B%5Bacid%5D%7D)
The optimum range of pH is pKa ± 1. The pKa is -log Ka = -log (8.4 × 10⁻⁴) = 3.1. The buffer would be more effective for pH between 2.1 and 4.1, especially around 3.1. So the best choice is (B) 3.
Answer:
4/15
Explanation:
15/15 - 11/15 = 4/15
If 11/15 is the probability that it'll rain tomorrow, then the rest should be the probability that it'll not rain tomorrow.