Aballoon is filled with 3.8 l of helium gas at stp. approximately how many moles of helium are contained in the balloon?

0.16964 moles ≈ 0.17 moles

Explanation:

At STP, one mole of a gas has a volume of 22.4 L.

1 mole = 22.4L

x mole = 3.8L

x =  ( 3.8 * 1 ) / 22.4

x = 3.8 / 22.4

x = 0.16964 moles ≈ 0.17 moles

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