A student determines the zinc content of a solution by first precipitating it as zinc hydroxide, and then decomposing the hydroxide to zinc oxide by heating. How many grams of zinc oxide should the student obtain if her solution contains 38.0 mL of 0.501 M zinc nitrate?
mols Zn(NO3)2 = M x L = ?
1 mol Zn in 1 mol Zn(NO3)2
1 mol ZnO in 1 mol Zn
g ZnO = mols ZnO x molar mass ZnO.
To determine the grams of zinc oxide obtained, we need to calculate the moles of zinc nitrate in the given solution and then use stoichiometry to find the moles of zinc oxide. Finally, we can convert the moles of zinc oxide to grams.
Let's break down the steps:
Step 1: Calculate the moles of zinc nitrate in the solution.
Moles = Molarity x Volume (L)
Moles = 0.501 mol/L x (38.0 mL / 1000 mL/L)
Moles = 0.501 mol/L x 0.0380 L
Moles of zinc nitrate = 0.019 mol
Step 2: Use stoichiometry to find moles of zinc oxide.
The balanced chemical equation for the decomposition of zinc hydroxide to zinc oxide is:
2 Zn(OH)2 --> 2 ZnO + 2 H2O
From the equation, we can see that it takes 2 moles of zinc hydroxide to produce 2 moles of zinc oxide.
Since zinc nitrate is used to produce the zinc hydroxide, and there is a 1:1 molar ratio between zinc nitrate and zinc hydroxide, the moles of zinc nitrate are equal to the moles of zinc hydroxide.
Therefore, the moles of zinc oxide obtained will also be 0.019 mol.
Step 3: Convert moles of zinc oxide to grams.
To convert moles to grams, we need to know the molar mass of zinc oxide (ZnO).
The molar mass of zinc (Zn) is approximately 65.38 g/mol, and the molar mass of oxygen (O) is approximately 16.00 g/mol.
Adding the molar masses together:
Molar mass of ZnO = 65.38 g/mol + 16.00 g/mol
Molar mass of ZnO = 81.38 g/mol
Now, we can calculate the mass of zinc oxide:
Mass = Moles x Molar mass
Mass = 0.019 mol x 81.38 g/mol
Mass = 1.55 g
Therefore, the student should obtain approximately 1.55 grams of zinc oxide from the given solution.
To determine the grams of zinc oxide produced, we need to follow a step-by-step process.
Step 1: Write and balance the chemical equation
The reaction for the decomposition of zinc hydroxide to zinc oxide is:
Zn(OH)2 → ZnO + H2O
Step 2: Determine the moles of zinc nitrate
To find the moles of zinc nitrate, we use the formula:
moles = concentration (M) x volume (L)
Given:
concentration (M) = 0.501 M
volume (L) = 38.0 mL = 0.0380 L
moles of zinc nitrate = 0.501 M x 0.0380 L = 0.019 Mols
Step 3: Determine the moles of zinc hydroxide
From the balanced chemical equation, we know that the stoichiometric ratio between zinc nitrate and zinc hydroxide is 1:1.
Therefore, the moles of zinc hydroxide will also be 0.019 moles.
Step 4: Determine the moles of zinc oxide
From the balanced chemical equation, we know that the stoichiometric ratio between zinc hydroxide and zinc oxide is also 1:1.
Therefore, the moles of zinc oxide will also be 0.019 moles.
Step 5: Convert moles of zinc oxide to grams
The molar mass of zinc oxide (ZnO) is 81.38 g/mol.
grams = moles x molar mass
grams = 0.019 moles x 81.38 g/mol ≈ 1.549 grams
So, the student should obtain approximately 1.549 grams of zinc oxide.