[javydog]

My understanding of a mole is that one mole of a substance contains 6.022 x 10²³ atoms. Is that right?

The question I'm wondering about is:

How many moles of lithium (Li) are in 1 mole of lithium hydride (LiH)?


I figured the answer would be half a mole but it says the answer is 1 mole of Li. How does this work?? Hopefully you understand my confusion but if not I can try to elaborate

[hypervalent_iodine]

Having taught this before, I understand that this can be a little tricky to get your head around at first, but it requires less mental gymnastics than you think. When it says 1 mole LiH, it is talking about the compound as a unit. Consider a single molecule of H₂O. If you took that single water molecule and broke it into its constituent parts, you wouldn't have (as per your logic) a third of an atom of oxygen and two thirds of an atom of hydrogen - that doesn't make any physical sense. Instead you have one atom of oxygen and 2 of hydrogen.

You have to look at it as a ratio of atoms per compound, and remember that a mole is a unit of molecules. IOW, what is true for 1 molecule is true for 6.02 x 10²³ molecules. In your case, for every 1 molecule of LiH, you have 1 lithium and 1 hydrogen. You can expand that to moles, and say that for every 1 mole of LiH, you have 1 mole of lithium and 1 of hydrogen. In my water example, for every 1 mole of H₂O, we have 2 moles of hydrogen and 1 of oxygen. In a more complicated example, say Mg(NO₃)₂, for every 1 mole of Mg(NO₃)₂, you have 1 mole of Mg, 2 moles of N, and 6 moles of oxygen.

[chenbeier]

My understanding of a mole is that one mole of a substance contains 6.022 x 10²³ atoms. Is that right?

The question I'm wondering about is:

How many moles of lithium (Li) are in 1 mole of lithium hydride (LiH)?


I figured the answer would be half a mole but it says the answer is 1 mole of Li. How does this work?? Hopefully you understand my confusion but if not I can try to elaborate

Lets make a Hamburger. You need 1 bread , 1 beefpaddy, 2 slice of cheese 1 tomato and 1 leaf of salad. This will give you 1 hamburger an not 6 hamburgers.

The same with chemicals. 1 mole lithium and 0.5 mol hydrogen H₂ gives 1 mol LiH.

[Borek]

My understanding of a mole is that one mole of a substance contains 6.022 x 10²³ atoms. Is that right?

No. 1 mole is 6.022 x 10²³ OBJECTS (be it atoms, ions, molecules). Your object in this case is a 'molecule' of LiH (LiH is ionic, so technically it doesn't contains typical molecules, hence '').

[javydog]

My understanding of a mole is that one mole of a substance contains 6.022 x 10²³ atoms. Is that right?

No. 1 mole is 6.022 x 10²³ OBJECTS (be it atoms, ions, molecules). Your object in this case is a 'molecule' of LiH (LiH is ionic, so technically it doesn't contains typical molecules, hence '').

OHHHH that completely explains it. thanks everyone