Only the third option is true: The individual substances in a mixture lose their original chemical properties. The atmosphere is most definitely not a solution and sugar is not a solvent.
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We can rewrite the equation KBr(aq) + AgNO3(aq) → AgBr(s) + KNO3(aq) into its net ionic equation into
K+ + Br- + Ag + + NO3- = AgBr + K + NO3-only aqueous solutions can dissociate. Spectator ions are present in both sides, hence these are K+ and NO3-. THe rules of assigning oxidation numbers is to identify the number of valence electrons of elements and may be arbitrary depending on the charge of the molecule.
Na3 = 23*3 = 69
P = 31
O4 = 16*4 =64
69+ 31+ 64 = 164g/mol
0.75mol = 0.75 * 164 = 123 g
