A.) Write a balanced chemical Eq'n for a reaction between MAGNESIUM & HYDROCHLORIC ACID.
Answer: Magnesium + Hydrochloric Acid
Mg (s) + 2 HCL (ag) ---- MgCl2 (aq) H2(g)
B.) Assuming 7.00 g of Magnesium completely react according to the above Eq'N, calculate the MOLES of hydrogen gas produced.
** I'm not sure how to do this** Can someone please help.
I don't understand how you would calculate the moles with a chemical equation given the 7.00 g of Magnesium.
Also, In this experiment hydrogen gas is collected over water and can be referred to as a "wet" gas. Why is "wet" gas as an appropriate term for this?
Is it because hydrogen gas is collected over water, which is wet?
The atomic mass of magnesium is 24, which means 24 grams of magnesium makes 1 mole.
On the other hand, the atomic mass of hydrogen is 1, so H2 will weigh 2 grams per mole.
From part A, which you correctly answered (except for the missing + sign), we conclude that 1 mole of Mg produces 1 mole of H2.
Therefore 24 g of Mg produces 2 g of H2. How many grams of H2 will be produced by 7 g of Mg?
You will need to use the accurate atomic masses from the periodic table to correctly answer part B. I used integers to make explanations simpler.
When hydrogen is collected over water, it is saturated (to its limit) with water vapour which exists as a "partial pressure" at the given ambient temperature and pressure. That means the partial pressure of H2 and the partial pressure of water vapour together will make one atmospheric pressure (under the lab conditions), thereby reducing the real volume of hydrogen. This has to be accounted for if we want to measure very accurately the quantity of hydrogen produced.
Thank you. Is there any chance that you could write it mathematically from your explanations. I have a hard time trying to decipher the work from standard form to numbers. I really appreciate the explanation though!
I do believe that the skill of transforming an actual problem to numbers is part of your training. However, I will work on this for this time.
The problem can be solved by proportions. Using:
"Therefore 24 g of Mg produces 2 g of H2. How many grams of H2 will be produced by 7 g of Mg? "
we first rewrite the proportions according to the exact atomic masses, namely
atomic mass for magnesium=24.305
atomic mass for hydrogen = 1.0079
(both from Wikipedia)
""Therefore 24.305 g of Mg produces 2*1.00794=2.01588 g of H2. How many grams of H2 will be produced by 7 g of Mg? ""
24.305 g : 2.01588 g
7.00 g : x g
Cross multiply,
7.00 ×2.01588 ÷ 24.305
= 0.580587 g
= 0.581 g (to three significant figures)
In chemistry (and physics), it is imperative to recognize the accuracy and the number of significant figures of the given information, as well as that of the answer.
In this example, the given information is 7.00 g, meaning accurate to 3 significant figures. The remaining information carries 5-6 significant figures, more accurate than the given information. So the answer must have exactly 3 significant figure, being the lowest of all relevant information, hence 0.581, to the nearest thousandth.
You were finding (g) but the question is asking to CALCULATE THE MOLES OF HYDROGEN GAS PRODUCED which I'm really confused about because I don't know how to go about this question now knowing the chemical reaction that occured. I'm sorry but can you find the Moles. or maybe I'm just missing something here.
Your answer came out to 0.581 g. It's saying Moles. or do I convert that?
I Really Really appreciate your help!
Sure! To calculate the moles of hydrogen gas produced, you need to use the given mass of magnesium and the balanced chemical equation.
Step 1: Convert the given mass of magnesium (7.00 g) to moles.
To do this, you need to know the molar mass of magnesium (Mg), which is approximately 24.31 g/mol.
The formula to calculate moles is:
moles = mass / molar mass
So, moles of magnesium = 7.00 g / 24.31 g/mol = 0.288 mol (rounded to three decimal places).
Step 2: Use the coefficients from the balanced chemical equation to determine the mole ratio between magnesium and hydrogen gas.
From the chemical equation:
1 mole of Mg reacts to produce 1 mole of H2 gas.
Step 3: Calculate the moles of hydrogen gas produced using the mole ratio.
Since the mole ratio is 1:1 between magnesium and hydrogen gas, the moles of hydrogen gas produced will be the same as the moles of magnesium.
Therefore, 0.288 moles of hydrogen gas are produced when 7.00 g of magnesium completely reacts with hydrochloric acid.
I hope this helps! Let me know if you have any further questions.