The weight percent of concentrated HClO4(aq) is 70.5% and its density is 1.67 g/mL. What is the molarity of concentrated HClO4

[HClO₄] = 11.7M

Explanation:

First of all we need to know, that a weight percent represents, the mass of solute in 100 g of solution.

Let's convert the mass to moles → 70.5 g . 1mol/100.45 g = 0.702 moles

Now we can apply the density to calculate the volume.

Density always refers to solution → Solution density = Solution mass / Solution volume

1.67 g/mL = 100 g / Solution volume

Solution volume = 100 g / 1.67 g/mL → 59.8 mL

To determine molarity (mol/L) we must convert the mL to L

59.8 mL . 1L/1000mL = 0.0598 L

Molarity → Moles of solute in 1L of solution → 0.702 mol / 0.0598 L = 11.7M

2b2t

explanation:

2b2t

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.