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.
Answer:
C: liquid
Explanation:
Liquid has the set volume as it cannot be compressed or 'expanded' like a gas. However, liquids will take the shape of the container you put them in so their shape can change.
Answer:
The products are CO₂ and H₂O.
The ballanced equation is this:
2C₄H₆ + 11O₂ → 8CO₂ + 6H₂O
Explanation:
In any chemical reaction, where you see that you have a compound reacting only with oxygen (O₂), you are in front of combustion.
Products in combustion are always water vapor and carbon dioxide.
Take a look to the methane combustion.
CH₄ + 2O₂ → CO₂ + 2H₂O
1 mol of methane reacts with 2 moles of oxygen to form 1 mol of CO₂ and 2 moles of water.
This is the combustion for an alkene where 2 moles of the alkene reacts with 11 moles of oxygen to make water and CO₂ like this:
2C₄H₆ + 11O₂ → 8CO₂ + 6H₂O
Answer:
Things like salt, sugar and coffee dissolve in water. They are soluble. They usually dissolve faster and better in warm or hot water. Pepper and sand are insoluble, they will not dissolve even in hot water.
i hope this helped you, have a great day
Answer:
D. a very fast run
Explanation:
Fermentation :
The second step of anaerobic respiration is fermentation. It involve the fermentation of pyruvate into lactic acid or alcohol depending upon the organism in which it is taking place. There is no ATP produced, however carbon dioxide is released in this step.
Anaerobic respiration in plants:
Anaerobic respiration in plants produced ethanol which if accumulate then cause the harmful effect in plants. It is also occur in some microorganisms such as yeast.
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
Anaerobic respiration in animals:
Anaerobic respiration in animals pyruvate converted into lactic acid and it is not as harmful as ethanol in plant if accumulate. It is produced during exercise because oxygen is not supplied to muscles. It can produce the cramps which can be cured with massage.
C₆H₁₂O₆ → 2C₃H₆O₃
