A container holds a sample of hydrogen gas at 300 K. The temperature decreased to 100 K and the pressure remained constant, and the volume changed to 1.0 L. What was the original volume?

Answer : The original volume of gas was, 3.0 L

Explanation :

Charles' Law : It is defined as the volume is directly proportional to the temperature of the gas at constant pressure and number of moles.

or,

where,

are the initial volume and temperature of the gas.

are the final volume and temperature of the gas.

We are given:

Now put all the given values in above equation, we get:

Thus, the original volume of gas was, 3.0 L

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2