Which one of the following is a correct expression for molarity?


Which one of the following is a correct expression

Answer

43. Correct expression for molarity = Moles of solute / Volume of solution in litres = Mole solute / L solution. In other units: mmol solute / mL solution Answer: C 44. 2.00 L of 0.100M soln of Ca3(PO4)2

  1. The solution contains 0.200 mol of Ca3(PO4)2:
To solve: No of moles of Ca3(PO4)2 = 2.00 L * 0.1 mol/L = 0.200 mol Hence True
  1. This solution contains 0.800 mol of oxygen atoms.
To solve:
No of moles of oxygen = 0.200 mol of Ca3(PO4)2 * 8 (No of oxygen per mol of Ca3(PO4)2) = 1.6 mol Hence false.
  • Could have been true for 1L of 0.100 mol of Ca3(PO4)2)
  1. 1.00 L of this solution is required to furnish 0.300 mol of Ca2+ ions.
    To solve:
No of moles of oxygen in 2L of 0.200M of Ca3(PO4)2 = 0.200 * 3 = 6 mol Thus to furnish 3 moles of oxygen we require half the volume i.e. = 1 L. Hence True
  1. There are 6.02 × 1022 phosphorus atoms in 500.0 mL of this solution. :
    To solve:
    No of phosphorous atoms = 0.500 L * 6.023*1023 * 0.2 mol/liter = 6.022*1022
Hence True.
  1. This solution contains 0.600 M of Ca2+.
To solve: No of moles of Ca2+ = 3(No od Ca2+ per mole of Ca3(PO4)2) * 0.200 M = 0.600 mol Hence true. 45.     0.200 M of K2SO4 solution is prepared by: Mol. Wt of phosphorous = 174.259 g/mol 1 L of 1M solution requires 174.259 g/mol K2SO4 Then: 20 ml of 5M K2SO4 solution = 1M solution; 1M solution diluted to 500 ml = 1 M / 500 ml = 0.200 M of K2SO4 46. Which solution has the same number of moles of NaOH as 50.00 mL of 0.100M solution of NaOH? 50.00 ml = 0.050 L of 0.100M sol = 0.005 mol NaOH. Then:
  1. 20.0 ml of 0.200 M = 0.020 L * 0.200 M = 0.004 mol NaOH
  2. 25.0 ml of 0.175 M = 0.025 L * 0.175 M = 0.437 mol Naoh
  3. 129 ml of 0.145 M = 0.129 L * 0.145 M = 0.018 mol NaOH
  4. 50.0 ml of 0.125 M = 0.050 L * 0.125 M = 0.625 mol NAOH
  5. 100 ml of 0.0500 M = 0.100 L * 0.0500 M = 0.005 mol NaOH

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