Without looking up any numerical data or doing calculations, predict whether the enthalpy change for each of the following reactions should be positive, negative, or zero. Reaction Enthalpy change HF()→ HF(s) F2 (g) → 2 F(g) CH4 (g) + 2 O2(g) → CO₂(g) + 2 H₂O(l) I2 (s) → 12 (g) 0000

Using Hess's Law to calculate net reaction enthalpy Nitric oxide (NO) can be formed from nitrogen, hydrogen and oxygen in two steps. In the first step, nitrogen and hydrogen react to form ammonia: N₂(g) + 3H₂(g) → 2NH3(g) In the second step, ammonia and oxygen react to form nitric oxide and water: 4 NH3(g) + 50₂(g) → 4NO(g) + 6H₂O(g) ΔΗ= - 905. kJ ΔΗ= - 92. kJ Calculate the net change in enthalpy for the formation of one mole of nitric oxide from nitrogen, hydrogen and oxygen from these reactions. Round your answer to the nearest kJ. kJ X S

Calculate the energy required to heat 202.0mg of cyclohexane from 18.4°C to 38.8°C . Assume the specific heat capacity of cyclohexane under these conditions is 1.85J·g−1K−1 . Be sure your answer has the correct number of significant digits.

A chemist carefully measures the amount of heat needed to raise the temperature of a 533.0 mg sample of CH,N from 53.8 °C to 68.3 °C. The experiment shows that 16.5 J of heat are needed. What can the chemist report for the molar heat capacity of CH,N? Round your answer to 3 significant digits. -1 - 1 J•mol • K x10

3. Hydrazine, N2H4, is a colorless liquid used as a rocket fuel. What is the enthalpy change for the process in which hydrazine is formed from its elements? N2(g) + 2H2(g) → N2H4(l) Use the following reactions, enthalpy changes, and Hess’s Law N2H4(l) + O2(g) → N2(g) + 2H2O(l); ΔrH° = −622.2 kJ H2(g) + ½O2(g) → H2O(l); ΔrH° = −285.8 kJ

Given that  2Al(s) +  3   2 O2(g)  →  Al2O3(s)   Δ H o   rxn = −1601 kJ/mol and  2Fe(s) +  3   2 O2(g)  →  Fe2O3(s)   Δ H o   rxn = −821 kJ/mol  calculate the standard enthalpy change for the following reaction: 2Al(s) + Fe2O3(s)  →  2Fe(s) + Al2O3(s) Enter your answer in scientific notation.      ×  10    kJ

Consider the thermochemical equation for the combustion of acetone (C3H₂O), the main ingredient in nail polish remover: C3H6O (1) + 4 O₂ (g) → 3 CO₂ (g) + 3 H₂O (g) ΔΗ° rxn = 1790 kJ If a bottle of nail polish remover contains 222 mL of acetone, what is the magnitude (the value) of heat released by the complete combustion of the acetone in the bottle? The density of acetone is 0.788 g/mL. The molar mass of acetone is 58.08 g/mol. The units are kJ. Do not include units in your answer.

Consider the hypothetical thermochemical equation 3 A + B → 2 C for which AH = 63.1 kJ/mol. Which one of the following reactions would have an enthalpy change of -2×AH? Here, AH refers to the enthalpy change of the original reaction. А) С — 3/2 А + 1/2 В B) 6 A + 2 B –→ 4 C С) 3/2 А + 1/2 В — С D) 4 C → 6 A + 2 B

A chemist carefully measures the amount of heat needed to raise the temperature of a 1.27kg sample of C4H6O2 from 41.3°C to 60.6°C. The experiment shows that 3.87 × 10^4J of heat are needed. What can the chemist report for the molar heat capacity of C4H6O2? Round your answer to 3 significant digits. = J⋅mol−1K−1

Consider these reactions, where M represents a generic metal. 2 M(s) + 6HCl(aq) →→→ 2 MC1₂(aq) + 3H₂(g) HCI(g) HCl(aq) H₂(g) + Cl₂(g) → 2 HCI(g) MCI, (s) → MCI, (aq) Use the given information to determine the enthalpy of the reaction 2 M(s) + 3 Cl₂(g) → 2 MC1₂ (s) 1. 2. 3. 4. ΔΗ = AH₁ = -694.0 kJ AH₂ = -74.8 kJ AH3= -1845.0 kJ AH4 = -375.0 kJ kJ