Mole - one of the most important concepts in chemistry - is a kind of link to go from the microworld of atoms and molecules in a normal macrocosm grams and kilograms.
In chemistry often have to consider large numbers of atoms and molecules. For fast and efficient calculation made using the weighing method. But it is necessary to know the weight of individual atoms and molecules. In order to identify the molecular weight must be added the weight of all atoms in the compound.
B. It is open to change as new evidence or data is discovered. If scientists discover new evidence, they must modify their theories to conform with the new data.
A. is <em>incorrect</em>. Scientific laws are so well established that there can be no exceptions.
C. is <em>incorrect</em>. A scientific theory is the collective judgement of scientists as to the best explanation for a phenomenon. A new observation may require modification of the theory.
D. is <em>incorrect</em>. Advancements in technology can provide new evidence that requires new explanations.
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Answer:
- <em>There are </em><u><em>4 moles</em></u><em> of chloride ions in 2 moles of calcium chloride.</em>
Explanation:
Start by writing the chemical formula of calcium chloride.
The suffix -ide in chloride means that chlorine is working as the ion Cl⁻, this is with oxidation state -1.
Calcium, being an alkaline earth metal, uses oxidation state +2, Ca²⁺
Then, two atoms of Cl are combined with one atom of calcium, because in this way each Cl atom will accept one electron from a Ca atom, which will donate its two valence electrons.
That is indicated in the chemical formula with subscripts: <u><em>CaCl₂</em></u>, meaning that each formula-unit of calcium chloride has 2 ions of chlorine and 1 ions of calcium, or twice the number of moles of chloride ion.
- 1 mol CaCl₂ : 1 mol Ca⁺ : 2 mol Cl⁻
⇒ 2 mol CaCl₂ : 2 mol Ca⁺ : 4 mol Cl⁻
Hence, there are 4 moles of chloride ions in 2 moles of calcium chloride.
Mass of Hydrogen gas required to react : 0.936 g
<h3>Further explanation</h3>
Reaction on Nitrogen gas and Hydrogen gas to produce Ammonia gas
N₂ (g) + 3 H₂ (g) ⇒ 2 NH₃ (g)
Conditions at T 0 ° C and P 1 atm are stated by STP (Standard Temperature and Pressure). At STP, Vm is 22.4 liters / mol
so mol Nitrogen for 3.5 L at STP :
From the equation, mol ratio of N₂ : H₂ = 1 : 3, so mol H₂ :
then mass of Hydrogen(MW= 2 g/mol) :
