Write and balance the following word reactions, and state if a precipitate is formed? Barium cyanide reacts with ammonium sulfate. Potassium hydroxide reacts with magnesium chloride.

1 Answer
Jul 6, 2017

These are regular double-replacement reactions, of the form

#AB + CD -> AD + CB#.

Basically, the cations switch, and charge is considered when determining the number of anions per cation / cations per anion. What is the formed solid called?


So, you should get:

#color(blue)(stackrel(color(red)(2+))"Ba"(stackrel(color(red)(1-))"CN")_2(aq) + (stackrel(color(red)(1+))("NH"_4))_2stackrel(color(red)(2-))("SO"_4)(aq) -> 2stackrel(color(red)(1+))("NH"_4)stackrel(color(red)(1-))("CN")(aq) + stackrel(color(red)(2+))"Ba"stackrel(color(red)(2-))("SO"_4)(s))#

Is this balanced? If not, you should fix it up.

  • Barium cyanide is reasonably soluble in water (#"18 g/100 mL water"# at #25^@ "C"#).

  • Barium sulfate is very poorly soluble (as we would expect from the guideline that sulfates are soluble except for those with #"Ag"^(+)#, #"Pb"^(2+)#, #"Ca"^(2+)#, #"Sr"^(2+)#, or #"Ba"^(2+)# cations).

  • All ammonium-based compounds are very soluble.


#color(blue)(2stackrel(color(red)(1+))"K"stackrel(color(red)(1-))"OH"(aq) + stackrel(color(red)(2+))"Mg"stackrel(color(red)(1-))("Cl"_2)(aq) -> 2stackrel(color(red)(1+))"K"stackrel(color(red)(1-))"Cl"(aq) + stackrel(color(red)(2+))"Mg"(stackrel(color(red)(1-))"OH")_2(s))#

Is this balanced? If not, you should fix it up.

  • All alkali-metal-based compounds are quite soluble in water.
  • Halides are as well (except for those with #"Hg"_2^(2+)#, #"Ag"^(+)#, or #"Pb"^(2+)# cations).
  • Hydroxides tend to be insoluble, and #"Mg"("OH")_2# is no exception (#"0.00064 g/100 mL water"# at #25^@ "C"#).