You are on a road trip through the mountains, and you notice that the cylinder in your car is not experiencing the same ideal expansion as when you originally calculated it at sea level. Rather than experiencing a change in volume of 488 mL as you calculated at sea level, it is experiencing a change in volume of 442 mL while driving through the mountains, with a total of 0.0727 g of gas phase molecules in the cylinder after the combustion reaction. Assuming that your car is still operating at 100% efficiency (as we assumed throughout the discussion problems on Tuesday), what is different now

1.solid

2.carbon dioxide

3.helium

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.