How Many Water Molecules in a Glass?

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A glass of water with a volume of 6.0 x 10*-4 cubic meters corresponds to a mass of 6.0 x 10*-4 kg, as water has a density of approximately 1000 kg/m³. To find the number of moles, the mass should be divided by the molecular mass of water, which is 18.0153 g/mol. The calculation involves converting the mass from kilograms to grams, yielding approximately 0.6 grams. After determining the number of moles, multiplying by Avogadro's number provides the total number of water molecules, which is approximately 2 x 10*19 molecules. Understanding the relationship between volume, mass, and density is crucial for accurate calculations.
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Homework Statement


A glass of water has a volume of 6.0 x 10*-4 cubic metres.
How many moles of water molecules are there in the glass?




Homework Equations





The Attempt at a Solution


I know it has something to do with Avogadro’s number but can’t figure out exactly what to do.

The weight of the water molecules will equal 6.0 x 10*-4 kg, right?
The molecular mass of water molecule is 18.0153 u.

So would it be 0.0006 kg divided by 18.0153u to give the nuber of moles?
Then with the number of moles, multiply by avogadros number to get the number of molecules?


Which gives me 2 x 10*19 molecules?

Any correction or verification greatly appreciated:smile:
 
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chawkdee said:

Homework Statement


A glass of water has a volume of 6.0 x 10*-4 cubic metres.

...
The weight of the water molecules will equal 6.0 x 10*-4 kg, right?

Hey there chawkdee :smile: Cubic meters are not a unit of weight are they? They are a unit of volume.

How can you relate the volume of water to its mass?
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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