PLEASE PLEASE HELP!

the number of grams of H2 in 1620 mL of H2 gas.

calculate at STP

The number of grams of in 1620 mL is 1.44 g

Explanation:

According to ideal gas equation:

P = pressure of gas = 1 atm (at STP)

V = Volume of gas = 1620 ml = 1.62 L  (1L=1000ml)

n = number of moles = ?

R = gas constant =

T =temperature =

Mass of hydrogen =

The number of grams of in 1620 mL is 1.44 g

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.