Combining oxygen gas and hydrogen gas to form liquid water is a chemical change. Pretty sure the rest are physical changes because a chemical change happens when a substance is altered completely. A physical change is when a substance keeps its components (I dunno what word to use) but just changes into a diferent shape. At least thats how my teacher explained it to me.
<span>The answer is D) 108 million kilometers. To solve this problem, you must perform a simple unit conversion calculation. 1 AU = 150,000,000 km is the conversion factor. Take the radius of Venus, .72 AU, and multiply it by 150,000,000 km/1 AU. You flip the conversion factor so that the units of the original distance in the numerator cancel the units in the denominator of the conversion factor. completing the calculation gives you 108,000,000 km</span>
While bond energies and bond enthalpies can be used to estimate the heat of reaction (enthalpy change of a reaction), H, the heat of neutralization is the heat released when 1 mole of water is generated by the reaction of an acid and a base (reaction).
For the same type of bond, bond enthalpies differ from compound to compound. For instance, the C-H bond enthalpy in methane is nearly identical to that of ethane, butane, etc. When we look up the bond enthalpy for a C-H bond in a table of bond enthalpies, the average number that results may only be accurate to two or three significant figures.
Each compound's enthalpies of production are listed, and those numbers take into account any minor variations in the enthalpies of each bond. Therefore, the result will be more accurate if you utilize formation enthalpies rather than average bond enthalpies to compute a given reaction's enthalpy change.
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