Single and Double Replacement Reactions

0:00How do atoms swap partners in a reaction? Here are two kinds of swap: single replacement and double replacement.

0:09Zinc is an element. Copper sulfate is a compound of copper and sulfate, a group of sulfur and oxygen atoms.

0:18In a single replacement, one element takes another's place in a compound. Here, zinc replaces copper.

0:26That is because zinc is more reactive than copper: it forms compounds more easily.

0:32No atoms are made or lost. Zinc, copper and sulfate just have new partners.

0:39In a beaker, a reddish-brown coat of copper forms on the zinc, and the blue colour fades.

0:46Can any metal replace any other? No. It depends on reactivity.

0:52Copper is less reactive than zinc, so it cannot take zinc's place. Nothing happens.

0:59A metal can only replace a less reactive metal.

1:03In a double replacement, two compounds swap partners.

1:07Take silver nitrate, where nitrate is a group of nitrogen and oxygen atoms, and sodium chloride.

1:15When the solutions mix, silver and sodium trade partners, making sodium nitrate and silver chloride.

1:22Both solutions are clear, yet a white solid appears. A solid that forms like this is called a precipitate.

1:32The precipitate is silver chloride. It is insoluble: it does not dissolve in water. Sodium nitrate stays dissolved.

1:41So in a single replacement, a more reactive element swaps in. In a double replacement, two compounds swap partners.