Question

How many moles of hydrogen ions are present in a 2L solution with a pH of 2.75​

Answer 1

3.556x 10^-3mol

Step-by-step explanation:

Using pH =-log [ H+], we can calculate the concentration of the hydrogen Ions.

pH =-log [ H+], pH = 2.75

2.75 = -log[H+], taking antilog of both sides

10^ — 2.75 = [H+]

[H+] =1. 778 x 10^-3M

Now that we have the concentration and also knows the volume, we can use the relation

Moles = concentration X volume

= 1. 778 x 10^-3M x 2L = 3.56x 10^-3mol

The moles of the hydrogen Ions is 3.56x 10^-3mol

Answer 2

We are given:

Volume = 2 L

pH = 2.75

Finding the concentration required:

we know that pH is just the negative log of the hydrogen ion concentration

pH = -log[H⁺]

we are given that the pH is 2.75

2.75 = -log[H⁺]

log[H⁺] = -2.75 [multiplying both sides by -1]

`10^(log[H]) = 10^(-2.75)`

[H⁺] = 1.78 * 10⁻³ Molar

Number of moles of Hydrogen ions:

[H⁺] = 1.78 * 10⁻³ Molar

which means that there are 1.78 * 10⁻³ moles of hydrogen ions in 1 liter solution

1.78 * 10⁻³ moles / L

multiplying and dividing by 2, we get:

3.56 * 10⁻³ moles / 2 L

Hence we need 3.56 * 10⁻³ moles of hydrogen ions