Which equation represents a physical change?

(1) H,0 (s) +6.01 kJH,0 (4)

(2) 2H, (g) +0,(g)--2H2O(g) + 483.6kJ

(3) H,(g) +12(g) + 53.0kJ →→ 2HI(g)

(4) N. (g) +20,(g) + 66.4k]— 2NO (9)

Select one:
a. reaction 1 only
b. reactions 1 &3
c. reactions 2&4
d. all reactions

Given the following reaction: c3h8+5o2=3co2+4h20 how many grams of co2 will be produced 7 g of c3h8 and 98 g of o2

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.

100 grams of molten lead (600°c) is used to make musket balls. if the lead shot is allowed to cool to room temperature (21°c), what is the change in entropy (in j/k) of the lead? (for the specific heat of molten and solid lead use 1.29 j/g⋅°c; the latent heat of fusion and the melting point of lead are 2.45 × 104 j/kg and 327°c, respectively.)