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!

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol