I have .8ml of 35% by weight hydrogen peroxide. The hydrogen peroxide density is 1.14 g/ml. how many moles of hydrogen peroxide are there?
You want to calculate the molarity of the H2O2.
35% w/w means 35 g H2O2/100 g solution.
Since mass = volume x density, then volume = mass/density = 100g/1.14 = about 87.7 mL.
mols in 35 g = 35/about 34) = about 1 mol
M = mols/L = about 1/0.0877 = ?
Then mols in 0.8mL = M x L.
Don't forget to convert 0.8 mL to L.
how many moles are in 4.6ml of 48% HBR? The 48% is by weight. I am not given the density this time.
I don't believe it can be done without the density. I think 48% w/v can be done without density but not w/w.
Thank you.
So it is w/v vs w/w that makes the difference
In this case yes.
If 48% w/v, that means 48g HBr/100 mL solution so 4.6 mL will have
48 g HBr x (4.6 mL/100 mL) = ? g and that gives grams in the volume you want which can be convert to mols by mol = g/molar mass. The problem with w/w is that you have no way of knowing how much the 4.6 mL weighs. With density you have a way of converting volume to weight. You have volume in w/v solutions and no conversion is necessary.
To determine the number of moles of hydrogen peroxide, we need to use the given information about the volume and density. Here's how you can calculate it:
Step 1: Calculate the mass of hydrogen peroxide.
Mass = Density × Volume
Given:
Density = 1.14 g/ml
Volume = 0.8 ml
Mass = 1.14 g/ml × 0.8 ml
Mass = 0.912 g
Step 2: Calculate the moles of hydrogen peroxide using its molar mass.
The molar mass of hydrogen peroxide (H2O2) is:
(2 × atomic mass of hydrogen) + (2 × atomic mass of oxygen)
Atomic mass of hydrogen = 1.008 g/mol
Atomic mass of oxygen = 16.00 g/mol
Molar mass of H2O2 = (2 × 1.008 g/mol) + (2 × 16.00 g/mol)
Molar mass of H2O2 = 34.014 g/mol
Step 3: Calculate the number of moles using the mass and molar mass.
Moles = Mass ÷ Molar mass
Moles = 0.912 g ÷ 34.014 g/mol
Moles ≈ 0.0268 moles
Therefore, there are approximately 0.0268 moles of hydrogen peroxide in 0.8 ml of 35% by weight hydrogen peroxide.