How is an emission spectrum of an element generated?

-when an electron in an atom is excited to a higher energy state.
-when an electron in an atom is in the excited state.
-when an electron in an atom returns from an excited state to a lower energy state.
-when an electron in an atom is in the ground state.

According to coulomb's law, how would the electrical force between particles change if the product of their electrical charge increased?

Which change in temperature is the smallest? a change of 1 thomson degree a change of 1 kelvin degree a change of 1 fahrenheit degree a change of 1 celsius degree

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.)