Calculate the ratio of ch3nh2 to ch3nh3cl required to create a buffer with ph = 10.24.

0.4167 = CH₃NH₂ / CH₃NH₃Cl

Explanation:

The CH₃NH₂ / CH₃NH₃Cl buffer has a pka of 10.62. Using Henderson-Hasselbalch formula:

pH = pka + log₁₀ [A⁻] / [HA]

Where A⁻ is weak base, CH₃NH₂, and HA is conjugate acid, CH₃NH₃Cl. It is possible to obtain the ratio of CH₃NH₂ / CH₃NH₃Cl to create a buffer with pH = 10.24, thus:

pH = pka + log₁₀ [A⁻] / [HA]

10.24 = 10.62 + log₁₀ [A⁻] / [HA]

-0.38 = log₁₀ [A⁻] / [HA]

0.4167 = [A⁻] / [HA]

0.4167 = CH₃NH₂ / CH₃NH₃Cl

I hope it helps!

quartz

explanation:

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.