Suppose you prepare a buffer by adding 0.157 mol of NaH2PO4 and 0.966 mol of Na2HPO4 to 1.0 L of water. What is the pH of the solution?

pH = 7,0

Explanation:

The buffer producing by the mixture of H₂PO₄⁻ and HPO₄²⁻ is:

H₂PO₄⁻ ⇄ HPO₄²⁻ + H⁺; pka: 7,21

Using the Henderson-Hasselbalch formula:

pH = pka + log₁₀ A⁻ / HA

Where: A⁻ is the conjugate base (HPO₄²⁻) and HA is the weak acid (H₂PO₄⁻)

Replacing the formula:

pH = 7,21 + log₁₀ HPO₄²⁻ / H₂PO₄⁻

As the moles of HPO₄²⁻ are 0,0966 and moles of H₂PO₄⁻ are 0,157:

pH = 7,21 + log₁₀  0,0966 / 0,157

pH = 7,0

I hope it helps!

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.