The density of hydrogen at STP is 0.09 g/l. What is the mass of the sample of hydrogen in exercise (36)?
The Correct Answer and Explanation is:
First, since you referred to “exercise (36)” but did not provide it here, I will explain the general method to calculate the mass of a hydrogen sample given its volume at STP, using the density you provided.
Correct Answer (generic form)
Mass of hydrogen (in grams) = volume of hydrogen (in liters) × density of hydrogen (0.09 g/l).
So if the volume of the hydrogen sample from exercise 36 is V liters, then:
Mass = V × 0.09 grams.
For example, if exercise 36 specifies a volume of 5 liters of hydrogen at STP, the mass would be:
Mass = 5 liters × 0.09 g/l = 0.45 grams.
Explanation:
To calculate the mass of a gas at standard temperature and pressure (STP), one of the simplest approaches is to use the relationship between mass, volume, and density. The density of hydrogen gas at STP is given as 0.09 grams per liter, meaning every liter of hydrogen weighs 0.09 grams. This relationship allows us to calculate the mass by multiplying the given volume of hydrogen by this density value.
This approach works well because gases at STP follow the ideal gas law closely, which standardizes the temperature to 0 degrees Celsius (273 K) and pressure to 1 atmosphere. Under these conditions, one mole of any ideal gas occupies 22.4 liters. Hydrogen, with a molar mass of approximately 2 grams per mole, will therefore have a density calculated by dividing its molar mass by its molar volume at STP: 2 grams divided by 22.4 liters equals approximately 0.089 grams per liter, which rounds to 0.09 grams per liter as given.
This density can now be used to quickly find the mass of any given volume of hydrogen gas. It is important to note that this calculation assumes the gas behaves ideally, which is a good approximation at STP. If the temperature or pressure deviates significantly from STP, the actual density could differ due to the real behavior of gases. However, for calculations at STP, this method is reliable and widely used in chemistry.