What do the numbers listed for an element on the periodic table represent?

a.) the number with a lower value is the number of protons and the number with a higher value is the mass.
b.) the number with a lower value is the number of neutrons and the number with a higher value is the number of protons.
c.) the number with a higher value is the mass and the number with a lower value is the combined number of protons and electrons.
d.) the number with a higher value is the number of protons and the number with a lower value is the number of neutrons.

Astudent is given a sample of a blue copper sulfate hydrate. he weighs the sample in a dry covered porcelain crucible and got a mass of 23.875 g for the crucible, lid, and sample. the mass of the empty crucible and lid was found earlier to be 22.652 g. he then heats the crucible to expel the water of hydration, keeping the crucible at red heat for 10 minutes with the lid slightly ajar. on colling, he finds the mass of crucible, lid, and contents to be 23.403 g. the sample was changed in the process to very light clue anhydrous cuso4. if there are again 100.0 g of hydrate, how many grams of cuso4 are in it? how many moles of cuso4? (hint: molar mass of cuso4 = 159.6 g / mole. what per cent of the hydrate is cuso4? you may convert the mass of cuso4 to moles.)

Which explanation is true about what happens to a ray of light when it strikes a mirror? a. a light ray is transmitted toward a mirror at a certain angle. the light ray is then reflected by the mirror at an equal angle but in the opposite direction of the transmitted ray. b. an incident ray strikes a mirror at an angle with a line perpendicular to the mirror. the light ray is then reflected at an angle equal to the angle of incidence but on the opposite side of the perpendicular line. c. a reflecting ray strikes a mirror at an angle with a line perpendicular to the mirror. the light ray is then refracted at an angle equal to the angle of the reflecting ray and on the same side of the perpendicular line. d. an incident ray strikes a mirror at an angle with a line parallel to the mirror. the light ray is then transmitted at an angle equal to the angle of incidence but on the opposite side of the parallel line. you so much! : -d take the time to try and answer correctly.

A1.5l container holds p.50 grams of an unknown gas at a pressure of 0.44 atm and a temperature of 50.c what is the molar mass of the unknown gas