Hannah just finished building a house of cards that stands four stories high. she is worried that it will fall down. which of the following statements must be true? a. a house of cards is too fragile and must fall down eventually due to gravity. b. if hannah adds another card to the house of cards, then it will fall down. c. as long as nobody touches the house of cards, it will remain standing. d. if no unbalanced force acts upon the house of cards, then it will remain standing forever.

There are two steps in the usual industrial preparation of acrylic acid, the immediate precursor of several useful plastics. in the first step, calcium carbide and water react to form acetylene and calcium hydroxide: cac2 (s) + 2h2o (g) → c2h2 (g) + caoh2 (s) =δh−414.kj in the second step, acetylene, carbon dioxide and water react to form acrylic acid: 6c2h2 (g) + 3co2 (g) + 4h2o (g) → 5ch2chco2h (g) =δh132.kj calculate the net change in enthalpy for the formation of one mole of acrylic acid from calcium carbide, water and carbon dioxide from these reactions. round your answer to the nearest kj .