How many grams of water are needed to react with 77.0 grams of CaCN2

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3

there are two significant figures.

the answer is a! (2.9 x 10^-18 j) hope i could someone. : )