How many moles of gas sample are 5.0 l container at 373k and 203kpa

For the purpose we will here use the ideal gas law:

p×V=n×R×T

V= 5.0 L

T= 373K

p= 203kPa

R is  universal gas constant, and its value is 8.314 J/mol×K

Now when we have all necessary date we can calculate the number of moles:

n=p×V/R×T

n= 203 x 5 / 8.314 x 373 = 0.33 mole
 

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water