How many total atoms are in 0.920 g of p2o5?

If you chip a tooth, most likely you will go to the dentist to have the missing material filled in. currently the material used to fill in teeth is a polymer that is flexible when put in, yet is hardened to the strength of a tooth after irradiation with blue light at a wavelength of 461 nm. what is the energy in joules for a photon of light at this wavelength?

When did stem cell research become known ? who discovered stem cell? what experiments or studies have been conducted so far?

What type of chemical reaction occurs between silver nitrate (agno3) and copper (cu)? the equation i was given is 2agno3 + cu —> 2ag+ cu(no3)2.