Answer Csl POa 5) Calculate the number of atoms present in 2.25 g of helium? Ans

Question

Answer Csl POa 5) Calculate the number of atoms present in 2.25 g of helium? Answer: 6) How many milliliters of water must be added to 2.05 liters of a 4.44 molar solution of NaOH to make the resulting solution 3.88 molar? Answer 7) How many electrons are present in the N-3 ion? Answer: Telertrons 8) How many moles of iron are contained in 5.22 X 1022 atoms of iron Answer MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 9) What is the mass number of an atom of gold that has 200 neutrons? A) 241 B 279 C) 252 D) 222 E) 297

Explanation / Answer

5.   no of moles    = W/G.A.Wt

                            = 2.25/4   = 0.5625moles

number of atoms   = no of moles * 6.023*10^23

                              = 0.5625*6.023*10^23   = 3.38*10^23 He atoms

6.   initial                                               Final

      M1   = 4.44M                                 M2 = 3.88M

      V1   = 2.05L                                   V2 =

              M1V1    = M2V2

                V2      =    M1V1/M2

                          =    4.44*2.05/3.88    = 2.35L   = 2350ml

7. N^3-    = 7+3 = 10 electrons

8.   6.023*10^23atoms   = 1 mole of Fe

      5.22*10^22 atoms     = 1mole*5.22*10^22/6.023*10^23   = 0.0866 moles of Fe

    

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