How many neutrons does a potassium atom have if its atomic number is 19 and it's mass number is 39

What pressure will be exerted by 0.675 moles of a gas at 25*c if it is in a 0.750-l container?

Agas can holds 2.0 gal of gasoline. what is this quantity in cubic centimeters?

Using the first volume and temperature reading on the table as v1 and t1, solve for the unknown values in the table below. remember to use the rules of significant figures when entering your numeric response.