3.) A certain tank contains a mixture of nitrogen, oxygen, and helium gases. The partial pressure of nitrogen gas is 503 mmHg. The partial pressure of oxygen gas is 481 mmHg. If the total pressure of the gas mixture is equal to 1291 mmHg.
What is the partial pressure of the helium gas?

c. 75.7

i think that is the right

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