Calculate the concentration of h3o+ in a solution that contains 5.5 × 10-5 m oh- at 25°c. identify the solution as acidic, basic, or neutral.
a. 1.8 × 10-10 m, acidic
b. 9.2 × 10-1 m, basic
c. 5.5 × 10-10 m, neutral
d. 9.2 × 10-1 m, acidic
e. 1.8 × 10-10 m, basic

The correct answer is option (e).

Explanation:

Concentration of hydroxide ions

The pOH of the solution is defined as negative logarithm of hydroxide ions of in an aqueous solution.

pH +pOH = 14

pH = 14-pOH

pH=14 - 4.259 = 9.741

The pH of the solution is defined as negative logarithm of hydronium ions of in an aqueous solution.

The solution is basic as pH of the solution is 9.741.

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