In a calorimetry experiment, a salt is dissolved in water within an insulating container. The temperature of the solution (surroundings) decreases from 25°C to 14°C. Given that the mass of the solution is 120 g, and the specific heat of the solution is 3.18 J/g°C, calculate the enthalpy change (in kJ) for the dissolving process. Be sure to give the correct sign for your answer, and identify the dissolving process as endothermic or exothermic. Group of answer choices

Asample of silver (with work function ? = 4.52 ev) is exposed to an ultraviolet light source (? = 200 nm), which results in the ejection of photoelectrons. what changes will be observed if: silver is replaced with copper (? = 5.10 ev) more photoelectrons ejected no photoelectrons are emitted fewer photoelectrons ejected more energetic photoelectrons (on average) less energetic photoelectrons (on average)

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)

What term describes technology that operates on an atomic level