Average human blood serum contains 18 mg of K+ Calculate:

a) the molar concentration for each of these species; use 1.00 g/mL for the density of serum.

I have worked as of this
(18 mg K+/100 mL)(1mL/1g)(1 mmol/39.10mg)(1g/1000mg).
But it seems that some units are not cancelled out when the desired units should be mol/liters for molar conc.

Please help me, any ideas

18 mg/100 mL x (1000 mL/1L) x (1 g/1000 mg) x (1 mL/1 g) x (1 mol/39.1 g) = ? mols/L

To calculate the molar concentration of K+ in blood serum, you need to convert the mass of K+ to moles and the volume of serum to liters.

The first step is to convert the mass of K+ (given in mg) to moles.

Given: 18 mg K+

1. Convert the mass to grams:
18 mg K+ x (1 g / 1000 mg) = 0.018 g K+

2. Convert the mass to moles using the molar mass of K+:
0.018 g K+ x (1 mol / 39.10 g) = 0.00046 mol K+

The next step is to convert the volume of serum (given in mL) to liters.

Given: 100 mL serum

3. Convert the volume to liters:
100 mL serum x (1 L / 1000 mL) = 0.1 L serum

Now, you can calculate the molar concentration (molarity) of K+ in blood serum by dividing the number of moles of K+ by the volume of serum in liters.

4. Calculate the molar concentration:
0.00046 mol K+ / 0.1 L serum = 0.0046 M K+

Therefore, the molar concentration of K+ in blood serum is 0.0046 M.

To calculate the molar concentration of K+ in human blood serum, we need to use the given information and the correct unit conversions.

First, convert the mass of K+ from milligrams (mg) to grams (g):

18 mg K+ = 18/1000 g K+

Next, convert the volume of serum from milliliters (mL) to liters (L) using the density of serum:

1 mL serum = 1 g serum
1 L serum = 1000 mL serum = 1000 g serum

Now, we can calculate the molar concentration, using the molar mass of K+:

Molar mass of K+ = 39.10 g/mol (as you correctly assumed)

Molar concentration (in mol/L) = (mass of solute in g) / (molar mass of solute in g/mol) / (volume of solution in L)

Molar concentration of K+ = (18/1000 g K+) / (39.10 g/mol) / (1000 g serum / 1000 mL serum)

Cancel out the units:

Molar concentration of K+ = (18/39.10)/(1000/1000) mol/L

Finally, solve for the molar concentration:

Molar concentration of K+ = 0.461 mol/L

Therefore, the molar concentration of K+ in human blood serum is approximately 0.461 mol/L.