If the actual yield of sodium chloride from the reaction of 8.3g of sodium and 4.5g of chlorine is 6.4g, what is the percent yield?
2Na(s) + Cl2(g)-->2NaCl(s)

A. 170%
B. 120%
C. 30%
D. 86%

Which of these would be caused by a chemical change? a) the formation of lava. b) sedimantary rock layering over time. c) metamorphic rock forming from igneous. d) metamorphic rock eroding to form sedimentary rock.

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?

An unknown substance has been shown to have weak covalent bonds. which of the following is most likely a property of this substance? a. high ph b. high conductivity c. low melting point d. low flammability