Copper is made of two isotopes. copper-63 is 69.17% abundant and it has a mass of 62.9296 amu. copper-65 is 30.83% abundant and it has a mass of 64.9278 amu. what is the weighted average mass of these two isotopes? show your work.

The weighted atomic mass of these two isotopes is 63.5679 amu. To calculate this first multiply Copper-63's mass of 62.9296 amu by .6917 which gets you 43.5284. Then multiply Copper-65's mass of 64.9278 by .3083 which gets you 20.0395. Then add 43.5284 and 20.0395 to get the final answer of 63.5679 amu.

Kerosene is lighter than water and so it floats on the water and continues to burn. Carbon (IV) oxide blankets the flame cutting off the supply of oxygen and extinguishing the fire.

Explanation:

As water is heavier than kerosene, it slips down permitting the kerosene to rise to the surface and continue to burn. Besides, the existing temperature is so high that the water poured on the fire would evaporate before it can extinguish the fire. Thus the kerosene fire cannot be extinguished with water.