Which of these is an indication that a chemical reaction has occurred?

select all that apply:

melting of a substance

boiling of a substance

formation of a new gas

formation of a precipitate

a new smell is given off

heat is released

What does x represent in the formula for the compound xcl4?

What is the ph of a 0.0010 m hno3? 1.0 3.0 4.0 5.0

The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.