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.

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"`).