Chemistry Answers

Calculate the freezing and boiling point of a solution prepared by dissolving 32.60 g of ferric chloride (FeCl3) in 0.4 m3 of water (H2O).

H2 and F2 react to form HF:

H2 (g) + F2 (g) → 2 HF (g)

the relevant bond dissociation energies, in kJ/mol, are: 

H—H: 436 F—F: 155 H—F: 567

Showing your work, calculate the value of ∆H for this reaction. Is this exothermic or endothermic?

A hypothetical reaction to form the compound A3B2 from its constituent elements is shown 

below. 

A2 (g) + B2 (g) → A3B2 (l) ∆H = –13.4 kJ/mol AB3 ∆S = –84.3 J/mol∙K 

Calculate the change in free energy (∆G) for this reaction at 298 K (25 °C, “room temperature”) using the formula ∆G = ∆H - T∆S. 

C2H2 (g) + 2 H2 (g) → C2H6 (g) + 42 kcal

a. Is this reaction exothermic or endothermic? Briefly explain your choice.

b. Would you expect entropy to increase or decrease for this reaction? Briefly explain.

Calculate the amount of heat released during the combustion of

a. 0.75 mole of C3H6O

b. 120g of C3H6O

What are the mass percentages of carbon and oxygen in carbon dioxide, ( CO2)?

If 1 more of O₂ react with 1 mole of N₂ - how many moles of NO₂ can be formed?

1.    A 1.000-g sample of ultrapure silicon was treated with an oxidizing agent and the resulting SiO₂, after proper collection and drying, weighed 2.1387-g. Calculate the %Si in the sample.