A runner weighs 687 N and 71% of this weight is water. (a) H

[Alice7979]

Homework Statement

A runner weighs 687 N and 71% of this weight is water. (a) How many moles of water are in the runner's body? (b) How many water molecules (H2O) are there?

Homework Equations

n = N/N_A
n= m/mass per mole
N_A = 6.022E23
F=ma
H: 2*1
O: 16

The Attempt at a Solution

a)
687/9.8=70.1 g
70.1 * .71 = 49.77 g of h20
49.77/18 u = 2.765

b) 6.022E23 * 2.765 = 1.665

 

[haruspex]

70.1 g

His mass is only 70.1 grams?! Check your units.

6.022E23 * 2.765 = 1.665

What happened to the E23?

 

[Nathanael]

The Attempt at a Solution

a)
687/9.8=70.1 g
70.1 * .71 = 49.77 g of h20
49.77/18 u = 2.765

Is this reasonable? A man who weighs 70.1 grams? Must be a world record...

(Posted at the same time as haruspex, oops)

 

[Alice7979]

I forgot the formula was in kg

 

[haruspex]

I forgot the formula was in kg

So does that change your answer?

 

[Alice7979]

So does that change your answer?

Yes it did, thanks

 

[haruspex]

(Posted at the same time as haruspex, oops)

Always happy to have corroboration.