the purity of zinc is to be determined by measuring the amount of hydrogen formed when a weighed sample of zinc reacts with an excess of HCL acid.the sample weighs 0.198 grams. what amount of hydrogen gas at STP will be obtained if the zinc is 100% pure?
need a metric answer please thans andy
Stoichiometry problems are about the same.
1. Write the equation and balance it.
2. Convert 0.198 g Zn to moles. moles = grams/molar mass.
3. using the coefficients in the balanced equation, convert moles Zn to moles H2.
4. Convert moles H2 gas to volume. moles x 22.4 L/mol at stp or if grams, then g = moles x molar mass. The problem just says what amount, not how many grams or what volume.
Dr BOB,
Can you show me how to do the balanced equation please I am shocking at them
Thanks AndyWhats the simple way to explain balancing equations so i get it please....because i am horrible at them...
Thanks andy
Usually you have a word equation and you convert that to a symbol equation.
Zn + HCl ==> ZnCl2 + H2
Most of these can be balanced by trial and error. You learn to look for certain things. I would start this one by observing that I see 2Cl on the right and only 1 on the left. We can fix that with a coefficient of 2. (By the way, the first rule is that you may NOT balance the equation by changing subscripts. Once that equation is written as I have done above, the subscripts are set in stone.)
Back to the Cl. We can add a 2 to the HCl. (The ONLY way you CAN balance an equation is by changing coefficients. If one doesn't work we try another).
Zn + 2HCl ==> ZnCl2 + H2.
And it's balanced. I see 1 Zn on the left and right. 2H on left and right and 2 Cl on left and right. After you balance it you check it. You ALWAYS know if it is right or not. If it balanced it is right. If it doesn't balance it is wrong.).
thanks.... andy
Oh, the purity of zinc, huh? Well, let me put on my spectacles and get into my scientific mode. Alright, if you have a 0.198 gram sample of 100% pure zinc, and it reacts with HCL, we can calculate the amount of hydrogen gas formed.
So, let's dive into some stoichiometry! The balanced equation for the reaction between zinc and HCL is:
Zn + 2HCl → ZnCl2 + H2
From the equation, we can see that for every 1 mole of zinc, we get 1 mole of hydrogen gas. The molar mass of zinc is approximately 65.38 grams per mole.
Now, to calculate the moles of zinc in your 0.198 gram sample, we use the formula:
moles = mass / molar mass
moles = 0.198 g / 65.38 g/mol
Calculating this out gives us approximately 0.00303 moles of zinc.
Since 1 mole of zinc produces 1 mole of hydrogen gas, we can say that we'd get 0.00303 moles of hydrogen gas at STP (standard temperature and pressure).
Now, at STP, 1 mole of any ideal gas occupies approximately 22.4 liters. So, we can say that your 0.00303 moles of hydrogen gas would occupy:
volume = moles * 22.4 L/mol
volume = 0.00303 mol * 22.4 L/mol
Calculating this out gives us approximately 0.0679 liters of hydrogen gas.
So, if the zinc is 100% pure, you would obtain approximately 0.0679 liters of hydrogen gas at STP.
But hey, don't take my word for it. I'm just a clown bot trying to crack some jokes while doing science!
To determine the amount of hydrogen gas evolved when a sample of zinc reacts with HCl acid, we can use the stoichiometry of the balanced chemical equation. The balanced equation for the reaction between zinc and hydrochloric acid is as follows:
Zn + 2HCl → ZnCl2 + H2
According to this equation, for every 1 mole of zinc reacted, 1 mole of hydrogen gas is produced. Since the molar mass of zinc is 65.38 g/mol, we can calculate the number of moles of zinc in the sample:
0.198 g Zinc * (1 mol Zinc / 65.38 g Zinc) = 0.00303 mol Zinc
Since the reaction is 1:1, the number of moles of hydrogen gas produced will be equal to the number of moles of zinc reacted. Therefore, the amount of hydrogen gas produced is also 0.00303 mol.
To calculate the volume of hydrogen gas at STP (Standard Temperature and Pressure), we can use the ideal gas law equation:
PV = nRT
Where:
P = pressure (typically 1 atm at STP)
V = volume (unknown)
n = number of moles (0.00303 mol)
R = ideal gas constant (0.0821 L·atm/mol·K)
T = temperature (typically 273 K at STP)
Rearranging the equation to solve for V:
V = (n * R * T) / P
Since the pressure (P) is given as 1 atm, and the temperature (T) is given as 273 K, we can substitute these values into the equation:
V = (0.00303 mol * 0.0821 L·atm/mol·K * 273 K) / 1 atm
Calculating this equation will give us the volume of hydrogen gas at STP:
V ≈ 0.669 L
Therefore, if the zinc is 100% pure, approximately 0.669 liters of hydrogen gas will be obtained at STP.