When NH4SCN is added to a solution of Fe3+ ions, the solution changes from yellow to orange. What is the best explanation for this color change?

The iron present in the solution is reduced because of the presence of SCN⁻ ions in solution

Explanation:

The clue in this problem is the color of the solution:

A solution of Fe³⁻ is yellow but when the Fe³⁺ is reduced by an oxidant to Fe²⁺ the solution change to orange color.

The SCN⁻ ion is a reducing agent than, in presence of a substance that can be reducted as Fe³⁺ ion will promote the reaction. That means the best explanation is:

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).