The standard enthalpy of ________ is the enthalpy change of reaction to form one mole of a substance from its elements under standard conditions of temperature and pressure.

Answers

Answer 1
Answer: Formation.
The standard enthalpy of formation occurs under the standard conditions of 298k and 1bar.

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What particles in an atom are involved in chemical reactions

Answers

Answer: Electrons

Explanation: In chemical reactions, elements and compounds change in order to form different substances. This changes can be:

1. oxidation state: which is define as the charge of the atom

2. bonding: atoms in a compound are bonded, this bonds can break so atoms rearrange to form different substances

In this changes electrons are involve. The charge depends on the amount of negative charge of electron respect to positive charge of proton in nucleus which remain the same, otherwise we would be talking about nuclear reactions.

Also, bonding depends on the electrons that atoms can give, receive or share to form ionic or covalent bonds.

What type of reaction occurs between Mg and HCl and explain why?

Answers

bonding is ionic for sure 
Mg has lost 2e,s to become Mg2+ 
and there are 2 Cl- 
the strong attraction between the Mg2+ and 2Cl- form the ionic bonding 

2.The image below shows two nitrogen atoms. For these two atoms to form a stable molecule, N2, how many electrons would have to be part of covalent bonds?

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D. 6 electrons

A single nitrogen atom has five electrons in its outer energy level to start, and will be most stable with an octet, or 8 electrons in its outer level.

Since N2 is a covalent bond, the lewis dot structure of  N2 would have a triple bond. Each bond contains 2 electrons, so if it has a triple bond it contains 6 electrons. 
Calculate the number of valence electrons of N2
N= 2x 5 = 10 
N2 has a total of 10 valence electrons, to become stable each N atom needs 8 electrons. 
So, therefore, 6 electrons would have to be a part of covalent bonds because they share 6 electrons in a triple bond. 

A sample of Ca(OH)2 is considered to be an Arrhenius base because it dissolves in water to yieldA. Ca2+ ions as the only positive ions in solution
B. H3O+ ions as the only positive ions in solution
C. OH– ions as the only negative ions in solution
D. H– ions as the only negative ions in solution

Answers

Answer : The correct option is, (C) OH^- ions as the only negative ions in solution

Explanation :

According to the Arrhenius concept, an acid is a substance that ionizes in the water to give hydronium ion or hydrogen ion (H^+) and a bases is a substance that ionizes in the water to give hydroxide ion (OH^-).

A sample of Ca(OH)_2 is considered to be an Arrhenius base because when it dissolves in the water to yield OH^- ions as the only negative ions in solution.

Hence, the correct option is, (C)

The answer is C. Arrhenius bases increase the concentration of OH- in solution.

What are the components of a phospholipid? 1) A phosphate group and two hydrophilic fatty acid tails 2) A phosphate group and two hydrophobic fatty acid tails 3) A phosphate group head and two hydrophobic fatty acid tails 4) A phosphate group head and two hydrophilic fatty acid tails

Answers

A phospholipid is composed of a polar, hydrophilic phosphate group 'head' and two hydrophobic (non-polar) fatty acid tails, where one tail is unsaturated (meaning it has a double bond between carbons, leading to a kinked shape).

Final answer:

Phospholipids are amphipathic molecules consisting of a hydrophilic (water-attracting) head group that contains a phosphate and is attached to a glycerol molecule and a hydrophobic (water-repelling) tail that contains two fatty acid chains. This structure permits different interactions based on charge and is crucial in forming biological membranes.

Explanation:

A phospholipid is an amphipathic molecule, or a molecule with both hydrophilic and hydrophobic components. This structure consists of a hydrophilic phosphatase-containing group (the head), and two hydrophobic fatty acid chains (the tails). The hydrophilic head group is typically made up of a phosphate group attached to a glycerol molecule. The hydrophobic tails are generally long hydrocarbon chains comprising of either saturated or unsaturated fatty acids.

This pattern allows for the dual-loving character of the phospholipid to interact differently with substances based on their charges and allows phospholipids to play a crucial role in the formation of biological membranes such as the plasma membrane.

Learn more about Phospholipid here:

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The unit of measure "mL" describes what property of a substance

Answers

It describes the property of a liquid.
i think its volume.......