Answer:
who lives in Barclays what?? this makes no sense
Explanation
Answer:
The amount of space an object occupies.
Explanation:
Answer:
- <u><em>It is positive when the bonds of the product store more energy than those of the reactants.</em></u>
Explanation:
The <em>standard enthalpy of formation</em>, <em>ΔHf</em>, is defined as the energy required to form 1 mole of a substance from its contituent elements under standard conditions of pressure and temperature.
Then, per defintion, when the elements are already at their standard states, there is not energy involved to form them from that very state; this is, the standard enthalpy of formation of the elements in their standard states is zero.
It is not zero for the compounds in its standard state, because energy should be released or absorbed to form the compounds from their consituent elements. Thus, the first choice is false.
When the bonds of the products store more energy than the those of the reactants, the difference is:
- ΔHf = ΔHf products - ΔHf reactants > 0, meaning that ΔHf is positive. Hence, the second statement is true.
Third is false because forming the compounds may require to use (absorb) or release (produce) energy, which means that ΔHf could be positive or negative.
Fourth statement is false, because the standard state of many elements is not liquid. For example, it is required to supply energy to iron to make it liquid. Thus, the enthalpy of formation of iron in liquid state is not zero.
Na2S2O3(aq) + 4Cl2( g) + 5H2O = 2NaHSO4(aq) + 8HCl(aq)
1)How many moles of HCl can form from 0.21 mol of Cl2?
0.21 mol Cl2 ( 8 mol HCl / 4 mol Cl2 ) = 0.42 mol HCl
2)How many moles of H2O are required for the reaction of 0.18 mol of Cl2?
0.18 mol Cl2 ( 5 mol H2O / 4 mol Cl2 ) = 0.225 mol H2O
3)How many moles of H2O react if 0.50 mol HCl is formed?
0.50 mol HCl ( 5 mol H2O / 8 mol HCl ) = 0.3125 mol H2O
The correct answer really is B.
If you are directed to break that rule then you better be in a high level chemistry class. When I taught things like that I insisted that students just wait until the chemical permeated the fume cabinet and even then I was always very nervous.
Sometimes you have to know when to ignore a bad direction. If you are working with chlorine, for example, you should be especially careful. That stuff was used in WWI as part of a chemical warfare technique. Many men suffered grotesque deaths by breathing it in, particularly if they were in trenches. Chlorine is heavier than air. It sinks to the lowest level.
