[T]

Hello what is the number of mols of HCl in this solution?

10 mL of a 35% hydrochloric acid (density 1.174 g/mL)

I don't really understand it. I interpreted it as 35% M but that gives you 0.0035 mol but the answer is 0.113.

Then I tried interpreting it as 35% by weight. This gives you 0.322.

Could someone tell me what 35% means?

Thanks.

[Borek]

Never heard about % M, what do you think it means?

Hard to say without context, but typically 35% HCl will mean 35% w/w.

Then I tried interpreting it as 35% by weight. This gives you 0.322.

Show how you got it.

[T]

% M in my opinion is the concentration (molarity).

I realized what I did wrong getting the 0.322. I multiplied 10 x 11.74 but forgot to multiply it by 0.35 before dividing it by the molar weight.

So when it says a percentage without mentioning molarity will it always mean w/w?

Thanks Borek

[Dan]

So when it says a percentage without mentioning molarity will it always mean w/w?

Yes, it should mean w/w unless otherwise specified (e.g. w/v).

[Borek]

% M in my opinion is the concentration (molarity).

Molarity is molarity, it is in no way related to %. Percentage is a fraction of a whole, a completely different concept.

[PhotoElectroMaterials]

If it is a 35% solution, it means 35g in 100g of water.  Since density of water is 1.  100g=100ml.
Hence 10ml of the solution contains 3.5g of HCl.
So number of moles = 3.5/36.45=0.096 moles of HCl in 10ml of water.

[Dan]

If it is a 35% solution, it means 35g in 100g of water. 

No it doesn't. 35 g HCl in 100 g of water is 35/135 = 26%.  It means 35 g in 65 g of water. 35% of the mass of the solution is HCl, the other 65% is water.
 

Since density of water is 1.  100g=100ml.
Hence 10ml of the solution contains 3.5g of HCl.
So number of moles = 3.5/36.45=0.096 moles of HCl in 10ml of water.

No, this is wrong. You have ignored the density of the solution (1.174 g/mL).

10.00 mL of solution has a mass of 11.74 g, 35% of which is HCl.

[T]

I see, thanks Dan

[PhotoElectroMaterials]

Thanks for the correction.

[Old_Doc48]

Hello what is the number of mols of HCl in this solution?

10 mL of a 35% hydrochloric acid (density 1.174 g/mL)

I don't really understand it. I interpreted it as 35% M but that gives you 0.0035 mol but the answer is 0.113.

Then I tried interpreting it as 35% by weight. This gives you 0.322.

Could someone tell me what 35% means?

Thanks.

35% +/- 2% is the typical concentration of HCl when purchased from manufacturer. It's concentration is 35% w/w = 35g HCl/100g Acid Soln = (35g/36.46g/mol)/[(100g)/(1.18g/ml)/(1000ml/liter)] = (0.9599mole/0.0848L) = 11.32 Molar
moles HCl in solution = Molarity of Concentrate x Volume of Solution (liters) = (11.32M)(0.010L) = 0.113 mole HCl(aq)

[skyblazer]

it is % v/v
 
35% of 10 mL is 3.5 mL

Since 1 mL is 1.174 g, the mass of 3.5 mL must be 3.5 x 1.174 which is 4.109 g

Now you have the mass of the HCl and you can divide it by its molar mass to solve for the number of mol in your solution (4.109 g    divided by   36.46 g/mol   = 0.113 mol)

[billnotgatez]

it is % v/v

Can you explain?

[AWK]

it is % v/v
 

Impossible. HCl is a gas. Nobody wants prepare water solution using pure liquid HCl. Liquid HCl boils at 190 K under atmospheric pressure.