To what temperature does a 250 ml cylinder containing 0.40 grams of helium gas need to be collected in order for the pressure to be 253.25 kPa?
Please show work.

T =76.13 K

Explanation:

Given data:

Temperature of gas = ?

Volume of gas = 250 mL(250/1000 = 0.25 L)

Mass of helium = 0.40 g

Pressure of gas = 253.25 kpa (253.25/101 = 2.5 atm)

Solution:

Formula:

PV = nRT

First of all we will determine the number of moles of helium.

Number of moles = mass/ molar mass

Number of moles = 0.40 g/ 4 g/mol

Number of moles = 0.1 mol

Now we will put the values.

R = general gas constant = 0.0821 atm.L/ mol.K

T = PV/nR

T =2.5 atm× 0.25 L /0.1 mol ×0.0821 atm.L/ mol.K

T = 0.625  /0.00821/K

T =76.13 K

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.