Answer:
a. PbO.
Explanation:
- The formula unit of a stable chemical compound should maintain that the overall charge of the compound is zero <em>(not charged)</em>.
- The formula unit of a compound is represented by the lowest ratio numbers of the ions forming the compound.
<em>Choice a:</em> is the right answer PbO
- That lead is divalent cation Pb²⁺ and O is considered as a divalent anion O²⁻.
- So, the formula unit contains Pb:O with a ratio of 1:1 (PbO)
<em>Choice b: </em>is a wrong choice Li₂B
- The lithium cation is a monovalent cation Li¹⁺ and boron is a trivalent cation B³⁺, so we can not do that.
<em>Choice c:</em> is a wrong choice Al₂Pb₃
- that Al is a trivalent cation Al³⁺ and Pb is a divalent cation Pb²⁺, so we can not do this for the two cations.
<em>Choice d:</em> is a wrong choice ClO
- that Cl may act as Cl¹⁺ and O acts as O²⁻, so the right formula unit should be Cl₂O.
Answer:
this may help you solve the problem! :D
Explanation:
Negative air ions (NAIs) have been discovered for more than 100 years and are widely used for air cleaning. Here, we have carried out a comprehensive reviewing on the effects of NAIs on humans/animals, and microorganisms, and plant development. The presence of NAIs is credited for increasing psychological health, productivity, and overall well-being but without consistent or reliable evidence in therapeutic effects and with controversy in anti-microorganisms. Reports also showed that NAIs could help people in relieving symptoms of allergies to dust, mold spores, and other allergens. Particulate matter (PM) is a major air pollutant that affects human health. Experimental data showed that NAIs could be used to high-efficiently remove PM. Finally, we have reviewed the plant-based NAI release system under the pulsed electric field (PEF) stimulation.
The correct answer is option D, that is, two new compounds.
Double displacement also known as double replacement reactions, metathesis or exchange reactions. It take place when two ionic compounds are exchanged forming two new compounds. One can consider the reaction as swapping the anions or the cations.
Water usually functions as the solvent for a double replacement reaction, and the products and reactants are generally ionic compounds, however, they can also be bases or acids. The example of a double replacement reaction is:
BaCl₂ (aq) + Na₂SO₄ (aq) = BaSO₄ (s) + 2NaCl (aq)
In this, the cations are Na⁺ and Ba²⁺, and the anions are SO₄²⁻ and Cl⁻. If the anions or cations are swapped, the products obtained are BaSO₄ and NaCl.
The answer is wood burring it causes smoke which worsens the air <span />
Answer:
Explanation:
a) In an exothermic reaction, the energy transferred to the surroundings from forming new bonds is ___more____ than the energy needed to break existing bonds.
b) In an endothermic reaction, the energy transferred to the surroundings from forming new bonds is ___less____ than the energy needed to break existing bonds.
c) The energy change of an exothermic reaction has a _____negative_______ sign.
d) The energy change of an endothermic reaction has a ____positive________ sign.
The energy changes occur during the bonds formation and bonds breaking.
There are two types of reaction endothermic and exothermic reaction.
Endothermic reactions:
The type of reactions in which energy is absorbed are called endothermic reactions.
In this type of reaction energy needed to break the bond are higher than the energy released during bond formation.
For example:
C + H₂O → CO + H₂
ΔH = +131 kj/mol
it can be written as,
C + H₂O + 131 kj/mol → CO + H₂
Exothermic reaction:
The type of reactions in which energy is released are called exothermic reactions.
In this type of reaction energy needed to break the bonds are less than the energy released during the bond formation.
For example:
Chemical equation:
C + O₂ → CO₂
ΔH = -393 Kj/mol
it can be written as,
C + O₂ → CO₂ + 393 Kj/mol