You want to divide by avagadros number (6.22 x 10^23). This will cancel the atoms unit and give moles, moles of Iridium. Now you want to calculate the atomic mass of Iridium which is in units of grams per mole. Multiply these two numbers and the moles will cancel giving you grams.
Setting up a dimension analysis type of thing helps tremendously. See what you have to cancel in order to get what you want. We canceled the atoms, then we canceled the moles, and then we got grams.
Answer 1) In the given reaction of sulfuric acid


On addition of nitrogen monoxide gas the reaction rate increases and more amount of product is formed.
So, it is clear that NO is the catalyst in this reaction.
Answer 2) This can be proven that NO is catalyst because it increases the rate of the reaction, but it is not consumed during the reaction, and it also gets regenerated at the end of reaction.
Hence, nitrogen mono oxide is considered as the catalyst in the given reaction.
Answer 3) It increases the rate of reaction by decreasing the activation energy of the reaction. Also it can be clearly seen in this reaction the NO is reacting with oxygen to lower the energy of activation. So, it is providing an alternative pathway for proceeding the reaction. This all confirms the assumptions of NO being the catalyst.

A. 3
From 0 to 6, a solution is acidic. 7 is neutral and from 8 to 14.. is basic
Answer:
Ksp = 8.8x10⁻⁵
Explanation:
<em>Full question is:</em>
<em>After mixing an excess PbCl2 with a fixed amount of water, it is found that the equilibrium concentration of Pb2+ is 2.8 × 10–2 M. What is Ksp for PbCl2?</em>
<em />
When an excess of PbCl₂ is added to water, Pb²⁺ and Cl⁻ ions are produced following Ksp equilibrium:
PbCl₂(s) ⇄ Pb²⁺ + 2Cl⁻
Ksp = [Pb²⁺] [Cl⁻]²
If an excess of PbCl₂ was added, an amount of Pb²⁺ is produced (X) and twice Pb²⁺ is produced as Cl⁻ (2X):
Ksp = [X] [2X]²
Ksp = 4X³
As X is the amount of Pb²⁺ = 2.8x10⁻²M:
Ksp = 4(2.8x10⁻²)³
<h3>Ksp = 8.8x10⁻⁵</h3>
2.187 is the answer to this question