Question

3.00×10⁻³ mol of HBr are dissolved in water to make 13.0 L of solution. What is the concentration of hydroxide ions, [OH⁻], in this solution? Express your answer with the appropriate units.

Answer 1

The concentration of hydroxide ions [OH-] in a solution where 3.00×10−3 mol of HBr is dissolved in 13.0 L of water is 4.33×10−12 M at 25°C.

Step-by-step explanation:

To calculate the concentration of hydroxide ions ([OH−]) when 3.00×10−3 mol of HBr are dissolved in water to make 13.0 L of solution, we first need to determine the concentration of hydronium ions ([H3O+]).

Since HBr is a strong acid, it will dissociate completely in water.

The moles of HBr will equal the moles of [H3O+], which is 3.00×10−3 mol. The concentration of [H3O+] is therefore 3.00×10−3 mol / 13.0 L = 2.31×10∔ M.

At 25 °C, the product of [H3O+] and [OH−] is always 1.0×10∑4 M2 (the ion product of water). We can use this relationship to find [OH−]:

[OH−] = 1.0×10∑4 M2 / [H3O+] = 1.0×10∑4 M2 / 2.31×10∔ M = 4.33×10−12 M

Therefore, the concentration of hydroxide ions in the solution is 4.33×10−12 M. Express your answer with the appropriate units.

Answer 2

The concentration of hydroxide ions in the solution is 2.99 × 10^(-3) M.

Step-by-step explanation:

To determine the concentration of hydroxide ions ([OH-]) in the solution, we need to use the concept of the self-ionization of water. In a neutral solution, the concentration of hydronium ions ([H3O+]) is equal to the concentration of hydroxide ions. Since the concentration of hydronium ions in the solution is not given, we need to calculate it by using the moles of HBr and the volume of the solution.

1. 
   
2. First, calculate the moles of HBr using the given molarity and volume: (3.00 × 10^(-3) mol/L) × (13.0 L) = 3.90 × 10^(-2) mol HBr
3. 
   
4. Since HBr is a strong acid, it completely dissociates in water to produce hydronium ions. Therefore, the concentration of hydronium ions is equal to the moles of HBr divided by the volume of the solution: [H3O+] = (3.90 × 10^(-2) mol) / (13.0 L) = 2.99 × 10^(-3) M
5. 
   
6. Since the concentration of hydronium ions is equal to the concentration of hydroxide ions in a neutral solution, the concentration of hydroxide ions is also 2.99 × 10^(-3) M.