Answer :
There are approximately 0.000486 moles of hydrogen present in the sample.
To find the number of moles of hydrogen present in the sample, you need to use the ideal gas law equation, which is PV = nRT where P is the pressure of the gas (in atm), V is the volume of the gas (in L), n is the number of moles of gas, R is the ideal gas constant, and T is the temperature of the gas (in K). First, you need to convert the pressure from torr to atm. You can do this by dividing the pressure in torr by 760, since 1 atm is equal to 760 torr. In this case, the pressure in atm would be: P = 764.5 torr / 760 = 1.0059 atm Next, you need to convert the volume from ml to L. You can do this by dividing the volume in ml by 1000, since 1 L is equal to 1000 ml. In this case, the volume in L would be: V = 30.42 ml / 1000 = 0.03042 L Finally, you need to convert the temperature from degrees Celsius to Kelvin. You can do this by adding 273.15 to the temperature in Celsius. In this case, the temperature in K would be:T = 25.58 degrees Celsius + 273.15 = 298.73 K Now that you have all the necessary values, you can plug them into the ideal gas law equation to solve for the number of moles of hydrogen: n = (PV) / (RT) = (1.0059 atm * 0.03042 L) / (8.31 J/mol*K * 298.73 K) = 4.86 x 10^-4 mol Therefore, there are approximately 0.000486 moles of hydrogen present in the sample
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