Calculating Electron Count and Net Charge in Water

[WGDawg3]

First post here, so I wanted to say hello first of all. Must admit this board seems quite helpful. Anyways, here's my problem I'm having issues with, any help would be great.

Water has a mass per mole of 18.0 g/mol, and each water molecule (H2O) has 10 electrons. (a) How many electrons are there in one liter (1.00x10^-3) of water? (b) What is the net charge of all these electrons?

I'm not even sure where to get started which is my main problem. Thanks again.

 

[Doc Al]

Hint: What's the density of water?

 

[Dick]

A mole of water contains Avogadro's number of molecules, 6.02*10^23 and it has a mass of 18g. A liter of water has a mass of 1000g. So how many moles in one liter? Hence how many molecules in one liter? Hence how many electrons in one liter? Etc. Does that get you started?

 

[WGDawg3]

A mole of water contains Avogadro's number of molecules, 6.02*10^23 and it has a mass of 18g. A liter of water has a mass of 1000g. So how many moles in one liter? Hence how many molecules in one liter? Hence how many electrons in one liter? Etc. Does that get you started?

I think I can maybe go with that... It's been a while since I've done anything physics related so I'm extremely rusty. Thanks, I'll be back quick with a response.

 

[WGDawg3]

OK, I took that info and did my best to work out the problem... I came up with 3.34x10^26 which was very close to one of the answer choices provided by my professor. Anyone mind double checking me?

The other 4 choices were:

4.25x10^25
1.62x10^26
1.08x10^25
5.05x10^26

 

[Dick]

That looks fine to me.

 

[WGDawg3]

Awesome, thanks a ton!