How many moles is 1.50 x 10^23 molecules nh3?

Tin has ten stable isotopes. the heaviest, 124sn, makes up 5.80% of naturally occuring tin atoms. how many atoms of 124sn are present in 82.0 g of naturally occurring tin? what is the total mass of the 124sn atoms in this sample?

Agroup of students is studying convection current. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other is in an area with warm air. after 10 minutes, the balloon are released from a height of 1 meter. which of the following to the students most likely observe? a) the warm balloon expands and rises. the cold balloon shrinks and sinks b) the balloon both rise. the cold balloon is larger than the warm balloon c) the cold balloon expands and rises. the warm balloon shrinks and sinks d) the balloon rise at the same rate. both balloons are the same size

What mass of natural gas (ch4) must you burn to emit 276 kj of heat?