Question #d0c80

2 Answers
Stefan V. · Media Owl
Apr 1, 2015

The thimble contains 3.3 * 10^(-4)3.3⋅10−4 moles of water.

To go from number of molecules to moles and vice versa, you can use Avogadro's number, which describes the number of atoms or molecules present in a mole of substance.

According to this, each mole contains exactly 6.022 * 10^(23)6.022⋅1023 atoms or molecules; in your case, 1 mole of water would contain 6.022 * 10^(23)6.022⋅1023 molecules of water.

Since 2.0 * 10^(20)2.0⋅1020 is a smaller number than 6.022 * 10^(23)6.022⋅1023, you'll have less than 1 mole of water in a thimble.

The exact value is

2.0 * 10^(20)cancel("molecules") * "1 mole"/(6.022 * 10^(23)cancel("molecules")) = 3.321* 10^(-4)"moles"2.0⋅1020molecules⋅1 mole6.022⋅1023molecules=3.321⋅10−4moles

Rounded to two sig figs, the answer will be

color(green)(3.3 * 10^(-4)"moles of water")3.3⋅10−4moles of water

Meave60
Apr 1, 2015

The thimble contains 3.3xx10^(-4)3.3×10−4 moles of water.

1 "mole water molecules" = 6.022xx10^23 "water molecules"1mole water molecules=6.022×1023water molecules

2.0xx10^20 cancel ("water molecules")xx(1 "mole water molecules")/(6.022xx10^23 cancel ("water molecules")2.0×1020water molecules×1mole water molecules6.022×1023water molecules = 3.3xx10^(-4) "moles water molecules"3.3×10−4moles water molecules

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