An experiment requires that each student use an 8.5 cm length of magnesium ribbon. How many students can do the experiment if there is a 570 cm length of magnesium ribbon available?

Answer:

[tex]7,16.10^{24}[/tex]

Explanation:

We know that in 1 mole of any substances there are [tex]6,02. 10^{23}[/tex] atoms

This number ([tex]6,02. 10^{23}[/tex]) is a constant that is known as the avogadros number

if we know how many atoms are in a mole of chromium to calculate how many there are in 11.9 moles we apply a simple rule of three

[tex]1 mol Cr\longrightarrow 6,02.10^{23} atoms\\ 11.9 moles Cr\longrightarrow x\\x=\frac{(11.9)(6,02.10^{23})}{1}\\ x= 7,16.10^{24} atoms[/tex]

In 11.9 moles of chrome there are [tex]7,16.10^{24}[/tex] atoms

Final answer:

Using the carbon-14 dating method, and knowing that the 14C in the fossil has decayed to 1/4 of its original amount, we can calculate that the plant was alive approximately 11,460 years ago.

Explanation:

In using carbon-14 dating to determine the age of a plant fossil, we utilize the known half-life of 14C which is approximately 5730 years. If the 14C has decayed to 1/4 of the original amount in the plant fossil, that means two half-lives have passed. As each half-life represents 5730 years, the age of the plant can be calculated by doubling this value. Therefore, we conclude that this plant was alive roughly 11,460 years ago.

Answer: 3 more electrons

Explanation: Generally elements with inert gas configuration are more stable. It is also called as Octet rule.

It tells that, elements which have electrons equal to atomic number of inert gases (2,8,10,18,36 etc) in their valency shell are exceptionally stable.

Here in our case, nitrogen has atomic number-7, 1s2 2s2 2p3

Here N has 5 electrons in valency shell , hence it needs 3 more electrons to get octet configuration.

So answer is 3 Electrons

The outer electron shell of nitrogen (N) contains 5 electrons. It would need to obtain 3 electrons to fill its shell with 8 electrons in order to have a stable outer electron shell.

An element's capacity to maintain its current state or withstand any changes under usual circumstances is referred to as stability. The fact that it guarantees an element's durability and versatility across a range of applications makes it a desirable property. Depending on the situation, stability can have a variety of meanings. Chemical stability, which refers to an element's resistance to reactions or decomposition when exposed to various chemical environments, is a crucial component of stability. Strong chemical bonds that take a lot of energy to break are common in elements with high chemical stability. The outer electron shell of nitrogen (N) contains 5 electrons. It would need to obtain 3 electrons to fill its shell with 8 electrons in order to have a stable outer electron shell.

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Orange juice is an acid, characterized by a pH level lower than 7. Its acidic nature is what gives it a sour taste, with citric acid and ascorbic acid being the main contributors. Lemon juice is usually even more acidic and sourer than orange juice. The correct answer is option: an acid.

Orange juice is an acid. The acidity of a substance can be measured by its pH level, with lower pH values indicating higher acidity. Because orange juice has a pH lower than 7, it is considered acidic. The sour taste of orange juice is due to citric acid and ascorbic acid (vitamin C), both of which are acids.

In contrast, substances with a pH higher than 7 are basic, with increased hydroxide ion (OH-) presence or proton (H+) acceptors. Water with a pH of 7 is considered neutral, neither acidic nor basic. Comparing orange juice to lemon juice in terms of acidity, lemon juice is typically more acidic due to its lower pH and higher concentration of citric acid, which is why it tastes more sour.

Answer : The reaction is endothermic in nature.

Explanation : A system of reactants which absorbs heat from the surroundings in an endothermic reaction has a positive ΔH reaction value, as the enthalpy of the products is higher than the enthalpy of the reactants of the system.

As the enthalpies of these reactions are greater than zero, they are called as endothermic reactions. Which absorbs the heat during the chemical reactions.

If the Hrxn of a reaction is positive then the reaction is endothermic reaction. In an endothermic reaction, heat is absorbed by the chemical reaction from the surrounding.

Reactants + heat --> Products

In the activation energy diagram the heat of the products is greater than the heat of the reactants in an endothermic reaction.

Your answer is d ) a complex system

The size of an astatine atom is predicted to be larger than that of tellurium.

Astatine and tellurium belong to the same group on the periodic table, but astatine has one more electron shell than tellurium, resulting in a larger atomic size. Astatine, with an atomic number of 85, has its electrons arranged in 6 electron shells, while tellurium, with an atomic number of 52, has electrons distributed across 5 electron shells. The increase in the number of electron shells for astatine leads to greater atomic size due to increased electron-electron repulsion, outweighing the increased nuclear charge.

Astatine's atomic radius is estimated to be greater than tellurium's due to the additional electron shell, leading to a larger atomic size. The trend across a period indicates a decrease in atomic radius from left to right due to increased nuclear charge and effective nuclear charge. However, within a group, atomic size generally increases going down the group due to the addition of electron shells. Hence, astatine, being located below tellurium in the same group (Group 16), is expected to have a larger atomic radius.

This prediction aligns with the periodic trend and the understanding of atomic structure, wherein the increase in electron shells as you move down a group results in larger atomic size, indicating that astatine would likely possess a larger atomic radius compared to tellurium.

The stage labelled C in the diagram is the G2 PHASE.

The cell cycle is divided into G1, S, G2 and M phases. The G2 phase is part of the phases of eukaryotic cell cycle. It is the second stage of interphase, it always occur after the completion of S phase. G2 is the stage, where the cell undergo more growth, produce more proteins and check the replicated DNA in order to verify that the cell is ready to enter into the mitosis phase.

Answer:

e2020 kids, D. G2 phase

Explanation:

Answer:

Cu

Explanation:

I got it right on my test.

The element with an atomic mass of about 63.5 amu is Copper, which has the chemical symbol Cu.

An atom with an average atomic mass of about 63.5 amu corresponds to the element Copper with the chemical symbol Cu. This is determined by consulting a periodic table where each element is listed with its respective atomic mass closest to the given value. The atomic mass is the weighted average of the masses of its isotopes, and in the case of copper (Cu), this is calculated from its two stable isotopes with mass numbers 63 and 65. Thus, the correct chemical symbol for the atom described with an atomic mass of 63.5 amu is Cu.

D) Chromium (Cr)

______________

Final answer:

To rank these compounds by their freezing points, we consider the van't Hoff factor which indicates the number of ions each compound forms. [tex]CoCl_3[/tex]  dissociates into the most ions, followed by [tex]K_2SO_4[/tex], and [tex]NH_4I[/tex] with the least, which corresponds to freezing points in ascending order: [tex]CoCl_3[/tex]  (lowest freezing point), [tex]K_2SO_4[/tex], and [tex]NH_4I[/tex] (highest freezing point).

Explanation:

To rank aqueous solutions by their freezing points based on equal concentrations and complete dissociation, we need to consider the number of particles each compound releases into the solution upon dissociation. The more particles that are present, the lower the freezing point. For [tex]K_2SO_4[/tex], which dissociates into three ions , [tex]NH_4I[/tex], which dissociates into two ions , and [tex]CoCl_3[/tex] , which dissociates into four ions the freezing points are affected by the van't Hoff factor (i), which is the number of particles into which a compound dissociates in solution.

Using this principle, we can deduce that:

Therefore, the order of decreasing freezing points is [tex]NH_4I[/tex] > [tex]K_2SO_4[/tex] >  [tex]CoCl_3[/tex]

Final answer:

1. Reactants are favored. 2. A chemical reaction rate measures the change in amount of reactant per unit of time. 3. When an equilibrium reaction makes more moles of gas than it consumes, increasing the pressure favors the reactants.

Explanation:

1. If Keq = 4 x 10^-7, the equilibrium constant, then reactants are favored because the Keq value is very small, indicating that the concentration of products is much lower than the concentration of reactants.

2. A chemical reaction rate measures the change in the concentration of a reactant or product per unit of time, so the correct answer is C) change in amount of reactant per unit of time.

3. In an equilibrium reaction that makes more moles of gas than it consumes, increasing the pressure favors the side with fewer moles of gas. Therefore, the equilibrium will shift to the left, favoring the reactants.

4. Adding more water to the equilibrium reaction CO2 + H2O <--> H2CO3 will result in the equilibrium being pushed in the direction of the reactants because adding more water will decrease the concentration of H2CO3, favoring the formation of more CO2 and H2O.

5. A catalyst increases the reaction rate by providing an alternative reaction pathway with a lower activation energy, which leads to more successful collisions between particles. Therefore, the correct answer is A) more collisions between particles, so more successful collisions.

6. To shift the reaction 4HCl(g) + O2(g) <--> 2Cl2(g) + 2H2O(g) to the right, the equilibrium can be shifted by increasing the pressure, which will favor the side with fewer moles of gas, in this case the products. Therefore, the correct answer is A) increase of pressure.

One mole each of CH4, NH3, H2S, and CO2 are added:

For CH4:

moles of C = 1

moles of H = 4 x 1 = 4

1 litre of water is = 55.5 moles of water.

so, in water:

moles of oxygen = 55.5

moles of hydrogen = 2 x 55.5 = 111

For NH3:

moles of N = 1

moles of H = 3 x 1 = 3

For H2S:

moles of H = 2 x 1 = 2

moles of S = 1

For CO2:

moles of C = 1

moles of  = 2 x 1 = 2

Now, add the total moles of each atom:

Hydrogen = 111 + 4 + 3 +1 = 119 moles

Oxygen = 55.5 + 2 = 57.5

Carbon = 1+1 = 2

Sulfur = 1

nitrogen = 1

What is mixture and compound?

In chemistry mixture is a combination of two or more different chemical elements which are not chemically bond. A mixture is the physical combination of two or more elements in which their individual identities are retained and it also mixed by solutions, suspension and colloids.

In chemistry compound is combination of two or more different elements which are chemically bond. So compound is held by chemical bond. A compound can't be separate by physical separation and after the mixture you can't identified that it is compound or not.

Therefore,Hydrogen = 111 + 4 + 3 +1 = 119 moles

Oxygen = 55.5 + 2 = 57.5

Carbon = 1+1 = 2

Sulfur = 1

Nitrogen = 1

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Answer:

potassium (k), because they are both alkali metals

Explanation:

Acetone is a covalent compound, whereas sodium chloride is an ionic compound.

Covalent compounds have strong bonds that do not break apart like ionic compounds do, and they do not conduct electric charge in solution.

Covalent compounds do not have strong attractions between molecules and so have very low melting points, unlike ionic compounds.

Answer:

3 scenarios:  

1. acetic acid, organic acid that comes from vinager

2. citric acid, that is present in some fruits

3. phosphoric acid , present in sodas

Explanation:

A weak acid is the one that partially transferres its proton (H+) to a water molecule ( partial dissociation), and usually a part of the original acid (HA) remains after the process of dissociation; that is why, a dissociation reaction of a weak acid is represented with an arrow of both ways.

[tex]HA ⇌ H^{+} +A^{-}[/tex]

As we can see, the acetic acid, citric acid and phosphoric acid are great examples of weak acid. Their pH is higher thanks to its low dissociation, and they can even be eaten in low concentrations.

Atomic Number, Ionic Radius, and First Ionization Energy are properties that depend on an element's structure, in particular its electron configuration. Atomic Number corresponds to an element's proton count, defining its identity and placement in the periodic table. Ionic Radius pertains to the size of an ion that forms when it loses or gains electrons. First Ionization Energy is the energy required to remove an electron from a neutral atom. These relationships reflect broader periodic trends.

The Atomic Number of an element is the count of protons in its nucleus. It determines the identity of an element and its placement on the periodic table. As the atomic number increases, the atomic size usually also increases because more energy levels are needed to accommodate more electrons.

The Ionic Radius refers to the size of an ion, which changes depending on whether it gains or loses electrons (and thus becomes an ion). Typically, cations (which lose electrons) are smaller than their parent atoms, while anions (which gain electrons) are larger because in both cases, the electron configuration changes, altering the electron-electron repulsion and consequently, the size of the ion.

The First Ionization Energy is the energy necessary to remove the first electron from a neutral atom. As atomic number increases, first ionization energy tends to increase because the outermost electrons are closer to the nucleus, thus more strongly attracted to the nucleus, making them harder to take away.

The relationships between Atomic Number, Ionic Radius, and First Ionization Energy are all part of the broader set of periodic trends, describing element's behavior across and down the periodic table.

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The species PO₄⁻³, ICl₃, SF₄, and ClO₄⁻¹ require an expanded valence shell in their Lewis Structures as they contain central atoms that go beyond the octet rule by bonding with more than four atoms.

The species that require an expanded valence shell to represent their Lewis structures are PO₄⁻³, ICl₃, SF₄, and ClO₄⁻¹. These molecules contain central atoms (Phosphorus, Iodine, Sulfur, and Chlorine respectively) that go beyond the octet rule by utilizing their d-orbitals to bond with more than four other atoms.

For example, in the case of PO₄⁻³ (Phosphate), the central atom (Phosphorus) is bonded to four Oxygen atoms and carries a formal charge, leading it to utilize its 3d orbitals and thus expanding its valence shell. Similarly for ICl₃, SF₄, and ClO₄⁻¹the central atoms exceed the octet rule, necessitating the expansion of their valence shell.

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