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

A. melting of a substance

B. boiling of a substance

C. formation of a precipitate

D. freezing of a substance

Jai was measuring the radioactivity of different radioactive isotopes. isotope a had a starting radioactive level of 50 g, and after 4 days it measured at 30 g. isotope b had a starting radioactive level of 75 g, and after 4 days it measured at 25 g.

4. (1 pt) If gravity always pushes down, what prevents a person from sinking down into the ground? A. Nothing prevents a person from sinking into the ground. B. Gravity only pushes with enough downward force to let a person touch the ground. C.

Based on the standard free energies of formation, which of the following reactions represent a feasible way to synthesize the product? A. 2C (s) + H2 (g) →C2H2 (g); ΔG∘f=209.2 kJ/molB. N2 (g) + 3H2 (g) →2NH3 (g); ΔG∘f=-33.30 kJ/molC.

What common household chemical is produced from the haber process?

When compared to sulfur-32, sulfur-34 has more - ?

3. A compound was analyzed and found to contain 9.8 g of nitrogen, 0.70 g of hydrogen, and 33.6 g of oxygen. What is the empirical formula of the compound?

A 126-gram sample of titanium metal is heated from 20.0°C to 45.4°C while absorbing 1.68 kJ of heat. What is the specific heat of titanium?

What pressure (in atm) will a sample of o2 gas occupy at 100.0 ml, if o2 has a volume of 25.00 ml at 2.0 atm?

What happens when francium and nitrogen are mixed

Which type of chemical reaction occurs in 2KClO3 Right arrow. 2KCl + 3O2