Best Answer
C) is the best description, although a scientific theory is not necessarily a "fact". They are, however, based on evidence.
A) is complete garbage.
B) is a good description of a scientific "law"- something that predicts how a certain event will occur without explaining why this is (for instance, the law of gravity accurately describes the gravitational forces between two bodies, but does not explain why these forces are there).
D) is a scientific "hypothesis"- an explanation for an observed phenomena that is yet to be proven.
Answer:
a. The reaction is endothermic.
Explanation:
The heat involved in a chemical reaction is given by the enthalpy change (ΔH), which is equal to the balance between the chemical bonds that are broken (release energy) and the chemical bonds that are formed (need energy):
ΔH ≅ bonds broken - bonds formed
If broken bonds > bonds formed ⇒ ΔH > 0 ⇒ endothermic reaction
Therefore, the reaction is endothermic (it requires energy).
hydrogen combines with sulfur is H2S
<span> hydrogen combines with
oxygen H2O</span>
<span>Hydrogen sulfide<span> <span>is the </span></span>chemical compound<span> <span>with the </span></span>formula <span>H<span>
2S</span></span>. It is a colorless gas<span> <span>with the characteristic foul odor of rotten </span></span>eggs<span>; it is heavier than air, very poisonous,
corrosive, flammable, and explosive; properties shared with the denser </span>hydrogen
chalcogenides</span>
<span> </span>
Given concentration of NaCl=15%
Means ,
In every 100g of Solution 15g of NaCl is present .
Now
So ,
<u>37.5g of NaCl present in 250g of solution.</u>
