A 0.500 g sample of He at STP has a volume that is one-half that of an unknown pure gas also at STP. The unknown pure gas sample has a mass of 36.5 g. What is the molar mass of the unknown gas?

The molar mass of the unknown gas which has a mass of 36.5 g is 146 g/mol

Mass of He = 0.5 g

Molar mass of He = 4 g/mol

At standard temperature and pressure (stp),

1 mole of He = 22.4 L

Therefore,

0.125 mole of He = 0.125 × 22.4

0.125 mole of He = 2.8 L

Volume of He = 2.8 L

Volume of unknown gas =?

Volume of He = ½ × Volume of unknown gas

2.8 = ½ × Volume of unknown gas

Cross multiply

Volume of unknown gas = 2.8 × 2

Volume of unknown gas = 5.6 L

22.4 L = 1 mole of unknown gas

Therefore,

5.6 L =

5.6 L = 0.25 mole of unknown gas.

Mole of unknown gas = 0.25 mole

Mass of unknown gas = 36.5 g

Molar mass of unknown gas =?

Therefore, the molar mass of the unknown gas is 146 g/mol

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answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.

practical process described pest part of scientific investigation.

because practical knowledge is powerful then therotical knowledge.