Use the provided reactions and their changes in enthalpy H2O(ℓ) ←→ H2(g) + 1 2 O2(g) ∆H = 285.8 kJ · mol−1 CH4(g) + 2 O2(g) ←→ CO2(g) + 2 H2O(ℓ) ∆H = −890.0 kJ · mol−1 CH4(g) ←→ Cgraphite(s) + 2 H2(g) ∆H = 74.9 kJ · mol−1 to find the change in enthalpy for the reaction CO2(g) ←→ Cgraphite(s) + O2(g) 1. 679.1 kJ · mol−1 2. −227.2 kJ · mol−1 3. −529.3 kJ · mol−1

What material does not melt at any temperature

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)

If one fission reaction of a uranium-235 atom produced two neutrons, how many neutrons would be released if the chain reaction occurred three more times?