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

## 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/NA
n= m/mass per mole
NA = 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
Homework Helper
Gold Member
2020 Award
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
Homework Helper

## 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)

Last edited:
I forgot the formula was in kg

haruspex
Homework Helper
Gold Member
2020 Award
I forgot the formula was in kg

Yes it did, thanks

haruspex