Answer:
a solution color becoming less intense due to dilution- is not an evidence of a chemical reaction
bubbles (gas formation) - evidence of a chemical reaction
explosion or fire - evidence of a chemical reaction
changes in color- evidence of a chemical reaction
precipitation- evidence of a chemical reaction
changes in temperature - evidence of a chemical reaction
a solid liquifying - is not an evidence of a chemical reaction
solution colors mixing - is not an evidence of a chemical reaction
Explanation:
A chemical change is not easily reversible and yields new substances. It is often accompanied by a loss or gain of heat.
In the answer section, i have shown some evidences that lead us to conclude that a chemical reaction has taken place. The occurrence of a chemical change often goes with the formation of new substances as earlier stated and any of these signs may accompany the process.
For instance, when a metal is dropped in dilute acid solution, bubble of hydrogen gas indicates that a chemical reaction has taken place.
compound name compound formula elements present
water H2O hydrogen (H) and oxygen (O)
ammonia NH3 nitrogen (N) and hydrogen (H)
carbon monoxide CO carbon (C) and oxygen (O)
carbon dioxide CO2 carbon (C) and oxygen (O)
Answer:
The moon to the direct right of the Earth relative to the Sun
Explanation:
These are two questions and two answers.
1) Question: Which of the following pairs of reactants will react together to produce water (H2O) as one of the products?
<span>Fe(OH)₃ and CuO
Cu(OH)₂ and H₂S
MgO and Ca(OH)₂
SO₃ and H₂O
</span>
<span>Answer:
</span>
<span>Cu(OH)₂ and H₂S
</span>
Justification:
1) Fe(OH)₃ and CuO: to form water Cu and Fe should react with each other. Being them two metals, they will not do that. So this reaction is not possible.
2) Cu(OH)₂ and H₂S: Being S a non metal and Cu a metal, they can react to form a the salt CuS, and water, as per this equation:
<span>Cu(OH)₂ + H₂S → CuS + 2H₂O
</span>
<span>
3) MgO and Ca(OH)₂: Being Mg and Ca two metals they will not react with each other, so this reaction is not feasible.
</span>
<span>4) SO₃ and H₂O: this is an acid oxide and water reaction which yields to an acid, as per this equation:
</span>
<span>SO₃ + H₂O → H₂SO₄
</span>
Which is not producing water
<span>2) Question: Based on reactivity, which of the following elements can replace
aluminum (Al) in a compound during a single replacement reaction?
B
Ca
Zn
Fe
</span>
Answer: Ca.
Justification:
Only an element more reactive than Al will replace it <span>in a compound during a single replacement reaction.</span>
You may predict that being Ca an alkalyne earth element it is more reactive than Al and so Ca will replace Al.
Else, you have to search a reactivity table, where you will find this order of reactivity among the metals:
Ca more reactive than Al
Al more reactive than Zn
Zn more reactive than Fe.
<span />
Being B a metalloid, its matallic character is low and it is less reactive than the other metals on the list.
Answer:
compounds
Explanation:
Substances made of two or more elements that are chemically joined together are called <u>compounds</u>.
<em>Generally, elements are substances that contain just a type of atom. Compounds, on the other hand, contain different atoms (of different elements) that are chemically linked together. The linkage is referred to as bonding. The bonding could be covalent, ionic, or hydrogen bonding.</em>
