12. In the modern periodic table, which of the following describes the elements with similar
2 answers:
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0.042 moles of Hydrogen evolved
<h3>Further explanation</h3>Given
I = 1.5 A
t = 1.5 hr = 5400 s
Required
Number of Hydrogen evolved
Solution
Electrolysis of water ⇒ decomposition reaction of water into Oxygen and Hydrogen gas.
Cathode(reduction-negative pole) : 2H₂O(l)+2e⁻ ⇒ H₂(g)+2OH⁻(aq)
Anode(oxidation-positive pole) : 2H₂O(l)⇒O₂(g)+4H⁻(aq)+4e⁻
Total reaction : 2H₂O(l)⇒2H₂(g)+O₂(g)
So at the cathode H₂ gas is produced
Faraday : 1 mole of electrons (e⁻) contains a charge of 96,500 C
Q = i.t
Q = 1.5 x 5400
Q = 8100 C
mol e⁻ = 8100 : 96500 = 0.084
From equation at cathode , mol ratio e⁻ : H₂ = 2 : 1, so mol H₂ = 0.042
Answer:
Explanation:
We are asked to find the mass of a number of platinum (Pt) atoms.
<h3>1. Convert Atoms to Moles </h3>First, we convert atoms to moles using Avogadro's Number or 6.022 × 10²³. This is the number of particles (atoms, molecules, formula units, etc.) in 1 mole of a substance. In this case, the particles are platinum atoms.
We will convert using dimensional analysis so we set up a ratio using the information we know (6.022 × 10²³ platinum atoms in 1 mole of platinum).
We are converting 4.99 ×10²¹ atoms of Pt to moles of Pt, so we multiply by this value.
Flip the ratio so the units of atoms of platinum cancel.
Divide.
Next, we convert moles to grams using the molar mass. This is the mass of 1 mole of a substance. This is found on the Periodic Table because it is equivalent to the atomic mass, but the units are grams per mole instead of atomic mass units. Look up platinum's molar mass.
- Pt: 195.08 g/mol
Set up another ratio using this new information (195.08 grams of Pt in 1 mole of Pt).
Multiply by the number of moles we just calculated.
The units of moles of platinum cancel.
The original measurement of atoms ( 4.99 ×10²¹ ) has 3 significant figures, so our answer must have the same. For the number we found, that is the hundredth place. The 6 in the thousandth place tells us to round the 1 up to a 2.
There are approximately <u>1.62 grams of platinum</u> in 4.99 ×10²¹ atoms of platinum.