Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Sodium chloride solution?

  1. Jun 15, 2004 #1

    Can sum1 help me with these two questions?

    How many grams of NaCl are required to make 0.30L of a 0.65mol/L soldium chloride solution?
    * for this question do i use the #moles = mass/molar mass?

    What volume os chlorine gas, measured at 10C and 101.3 kPa, is required to react completely with 10.20 g of KOH in following reaction:
    Cl2 + 2KOH -> KCl + KClO + H2

    if you noe how to do this, can u please reply? thanxz!!!
  2. jcsd
  3. Jun 16, 2004 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    1) Find the number of moles of NaCl by multiplying concentration and volume. Now since each mole of NaCl requires one mole of Na, the above number equals the number of moles of Na required. Now to convert this to grams, multiply the number of moles by the atomic weight (which is the same as the molar mass for an element).

    2) Find # moles of KOH using the mass/molar mass calculation. Now, the equation says that each mole of Cl2 reacts with 2 moles of KOH, so divide the above number by 2 to get the # moles of Cl2. Fianlly, use the ideal gas law, PV = nRT, to convert moles to volume. Be careful with units.
  4. Jun 16, 2004 #3


    User Avatar
    Science Advisor
    Homework Helper

    First one, you are on the right track. Multiply your volume (L) by your concentration (mol/L) to find out how many moles you have. That answer is multiplied by your molar mass (grams/mole) to get the number of grams.

    The second one is just slightly more complicated. You have half as many moles of chlorine gas as you do KOH. You need to convert the mass of KOH to moles of KOH (using the molar mass of KOH). Divide that by 2 to get the number of moles of chlorine gas.

    Once you have the number of moles of chlorine gas, you have to plug that into your ideal gas equation to get the volume (you've been given the temperature, which has to be converted to Kelvin, the pressure, which has to be converted to atmospheres, and you should know your gas constant, R, which is 0.082057, so you have the variables needed to solve for volume.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook