A solid product obtained from the reaction of solutions of mercuric nitrate and potassium bromide yielded the following mass spectral data. Identify the compound and assign all masses in the spectrum according to isotopic content.

Ligand X forms a complex with both cobalt and copper, each of which has a maximum absorbance at 510 nm and 645 nm. respectively. A 0.243 g sample containing cobalt and copper was dissolved and diluted to a volume of 100.0 mL. A solution containing ligand X was added to a 50.0 mL aliquot of the sample solution and diluted to a final volume of 100.0 mL. The measured absorbance of the unknown solution was 0.503 at 510 nm and 0.368 at 645 nm, when measured with a 1.00 cm cell. The molar absorptivities of the cobalt and copper complexes at each wavelength are shown in the table. Molar Absorptivity (c. M-'cm-¹) Wavelength [Co² = A, nm [Cu²+] = 510 645 3.125 x10-5 Incorrect Co 2.867 x10-5 3.7630 x 10² What is the concentration of cobalt and copper in the final diluted solution? 1282 Cu 5707 18090 M M

When the Nickel (II) ion reacts with ammonia, most students notice  a colour change occurring. Can you explain what the reaction is? And what colour they would see?