Physical Chemistry

posted by .

Calculate the concentrations of each of the following solutions.
(a) the molality of chloride ions in an aqueous solution of iron(III) chloride for which xFeCl3 is 0.0195

(b) the molality of hydroxide ions in a solution prepared from 9.16 g of barium hydroxide dissolved in 179 g of water

(c) the molality of 12.70 M NH3(aq) with a density of 0.9519 g·cm-3

I have repeatedly tried to figure out how to solve these, but I am getting something wrong. I know molality is mol solute/kg solvent. I'm especially having trouble with the second question. Please don't just give me the answer--try to explain how you solved it. An answer would be helpful so I can compare what I come up with though. Thanks!!

  • Physical Chemistry -

    For a.
    Assume you have 1 mole of solution; therefore, you will have 0.0195 moles FeCl3 and 0.9805 moles H2O.
    0.9805 moles x molar mass = 17.663 g H2O and since molality = moles/kg solvent that will be 0.0195 moles/0.017663 = ??m. Round to 3 s.f.
    Check my arithmetic.

  • Physical Chemistry -

    Got it. for A i was using molar mass for FeCl3 instead of water..oops. I solved C...but I am still confused with the second question of anyone can help me out... Thanks!

  • Physical Chemistry -

    the answer for a was actually incorrect

  • Physical Chemistry -

    The answer to a is not incorrect if you re-read the problem. What you have calculated is molality of FeCl3, the problem asks for molality of Cl^-, so multiply the final answer you had by 3.

    For #2, I think you reposted this later and I responded. If you still have questions or think there was an error, please repost a new post at the top of the page and I'll take a look at it.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry

    When hypochlorite ions act as an oxidizing agent, hydroxide ions are formed. What will this do to iron (II) or to iron (III) ions?
  2. chemistry.

    How many grams of sodium chloride are there in 55.00 Ml of a 1.90 M aqueous solution of sodium chloride?
  3. Chemistry

    I still need help with this problem... Calculate the concentration of the solution the molality of hydroxide ions in a solution prepared from 9.16 g of barium hydroxide dissolved in 179 g of water I do not know how to approach this...I …
  4. Chemistry

    A dilute electrolyte solution is prepared by dissoving iron (III) chloride in water. It is found to have a freezing point of -2.10 degrees C. Calculate the molality of the solution.
  5. Chemistry (moles)

    A 1.00L sample of seawater contains 19.4g of chloride ions, 10.8 g of sodium ions, and 1.29 g of magnesium ions. How many more moles of chloride ions would be needed to make neutral salts of all the cations in solution?
  6. Chemistry

    The problem ask what is the mass of iron(iii) chloride contains 2.35 x 10^23 chloride ions. I understand the molar mass is 162.20 g/mol. - 2.35 x 10^23 chloride ions would be around 0.39 moles. - The work that my teacher gave me is …
  7. chemistry

    for an aqueous solution having Calcl2 (2molar) and Mgcl2 (5molal) and specified gravity of solution is 1.145 calculate molality of chloride ion and molality if chloride ion.
  8. Chemistry (reposts#2)

    A solution is prepared by dissolving 5.00 g of ferric chloride in enough water to make 500.0 mL of stock solution. A 50.0 mL aliquot (portion) of this stock solution is then removed and added to 75.0 mL of water. Calculate the concentrations …
  9. Science

    Which of the following is the pH when the concentrations of hydrogen ions and hydroxide ions in an aqueous solution are equal?
  10. CHEMISTRY

    *Consider a 0.15 m strontium chloride aqueous solution. a. Determine the molality (in m) of all solutes in the solution. Assume that strontium chloride completely ionizes when dissolved in water. All solutes means all cations and anions. …

More Similar Questions