Which statement
about Niels Bohr's atomic model is true?
Higher orbits have lower energies.
Each orbit has a specific energy level.
&
Electrons can exist in any energy level.
Orbits close to the nucleus have no energy.

Answer:

1. CrCl₃     2. MnO₂     3. MgCO₃

Explanation:

For a compound to be neutral, we need the same number of positive charges and negative charges.

1. Cr³⁺ ions and Cl⁻ ions. We will need 1 Cr³⁺ cation and 3 Cl⁻ anions. The chemical formula is CrCl₃.

2. Mn⁴⁺ ions and O²⁻ ions. We will need 1 Mn⁴⁺ cation and 2 O²⁻ anions. The chemical formula is MnO₂.

3. Mg²⁺ ions and CO₃²⁻ ions. We will need 1 Mg²⁺ cation and 1 CO₃²⁻ anion The chemical formula is MgCO₃.

Answer:

Option D. 4

Explanation:

The oxidation number of nitrogen (N) in NO₂ can be obtained as follow:

Oxidation number of O = –2

Oxidation number of N =?

N + 2O = 0

N + 2(–2) = 0

N – 4 = 0

Collect like terms

N = 0 + 4

N = +4

Thus, the oxidation number of nitrogen (N) in NO₂ is +4

Answer:

a

Explanation:

Answer: The mass of [tex](NH_4)_2SO_4[/tex] produced is 9910.5 g

Explanation:

Molarity is calculated by using the equation:

[tex]\text{Molarity}=\frac{\text{Moles}}{\text{Volume}}[/tex] ......(1)  

Molarity of [tex]H_2SO_4[/tex] = 3.0 M

Volume of solution = 25.0 L

Putting values in equation 1, we get:

[tex]\text{Moles of }H_2SO_4=(3.0mol/L\times 25.0L)=75mol[/tex]

The ideal gas equation is given as:

[tex]PV=nRT[/tex] .......(2)

where,

P = pressure of the gas = 0.68 atm

V = volume of gas = [tex]3.1\times 10^3L[/tex]

n = number of moles of gas = ? moles

R = Gas constant = 0.0821 L.atm/mol.K

T = temperature of the gas = 298 K

Putting values in equation 2, we get:

[tex]0.68atm\times 3.1\times 10^3L=n\times 0.0821L.atm/mol.K\times 298K\\\\n=\frac{0.68\times 3.1\times 10^3}{0.0821\times 298}=86.16mol[/tex]

For the given chemical equation:

[tex]NH_3(g)+H_2SO_4(aq)\rightarrow (NH_4)_2SO_4(aq)[/tex]

By stoichiometry of the reaction:

If 1 mole of [tex]H_2SO_4[/tex] reacts with 1 mole of [tex]NH_3[/tex]

So, 75 moles of [tex]H_2SO_4[/tex] will react with = [tex]\frac{1}{1}\times 75=75mol[/tex] of [tex]NH_3[/tex]

As the given amount of [tex]NH_3[/tex] is more than the required amount. Thus, it is present in excess and is considered as an excess reagent

Thus, [tex]H_2SO_4[/tex] is considered a limiting reagent because it limits the formation of the product.

By the stoichiometry of the reaction:

If 1 mole of [tex]H_2SO_4[/tex] produces 1 mole of [tex](NH_4)_2SO_4[/tex]

So, 75 moles of [tex]H_2SO_4[/tex] will produce = [tex]\frac{1}{1}\times 75=75mol[/tex] of [tex](NH_4)_2SO_4[/tex]

The number of moles is defined as the ratio of the mass of a substance to its molar mass. The equation used is:

[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex]

We know, molar mass of [tex](NH_4)_2SO_4[/tex] = 132.14 g/mol

Putting values in above equation, we get:

[tex]\text{Mass of }(NH_4)_2SO_4=(75mol\times 132.14g/mol)=9910.5g[/tex]

Hence, the mass of [tex](NH_4)_2SO_4[/tex] produced is 9910.5 g

Answer:

1.9 × 10² g NaN₃

1.5 g/L

Explanation:

Step 1: Write the balanced decomposition equation

2 NaN₃(s) ⇒ 2 Na(s) + 3 N₂(g)

Step 2: Calculate the moles of N₂ formed

N₂ occupies a 80.0 L bag at 1.3 atm and 27 °C (300 K). We will calculate the moles of N₂ using the ideal gas equation.

P × V = n × R × T

n = P × V / R × T

n = 1.3 atm × 80.0 L / (0.0821 atm.L/mol.K) × 300 K = 4.2 mol

We can also calculate the mass of nitrogen using the molar mass (M) 28.01 g/mol.

4.2 mol × 28.01 g/mol = 1.2 × 10² g

Step 3: Calculate the mass of NaN₃ needed to form 1.2 × 10² g of N₂

The mass ratio of NaN₃ to N₂ is 130.02:84.03.

1.2 × 10² g N₂ × 130.02 g NaN₃/84.03 g N₂ = 1.9 × 10² g NaN₃

Step 4: Calculate the density of N₂

We will use the following expression.

ρ = P × M / R × T

ρ = 1.3 atm × 28.01 g/mol / (0.0821 atm.L/mol.K) × 300 K = 1.5 g/L

Answer:

d

Explanation:

cuaase that it sirhal

The chemical formula PbCl₂(s) represented by:

A) a substance

The chemical formula PbCl₂(s) represents a substance. A substance is a single, pure chemical entity with a definite composition. It can be an element, a compound, or an alloy.

A solution is a homogeneous mixture of two or more substances. A homogeneous mixture is a mixture in which the components are evenly distributed throughout the mixture.

A heterogeneous mixture is a mixture in which the components are not evenly distributed throughout the mixture.

A reaction is a process in which one or more substances are transformed into one or more new substances.

Therefore, the chemical formula PbCl₂(s) represents a substance, and the answer is (A).

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Answer:

Storage solution; deionized water; stabilizes.

Explanation:

The pH scale measures the concentration of hydrogen ions in acidic and alkaline solutions.

In chemistry, it literally means power of hydrogen ions and it is a measure of the molar concentration of hydrogen ions in a particular solution, thus specifying the acidity, neutrality or basicity of chemical solutions.

Mathematically, the pH of a solution is given by;

[tex] pH = -log_{10}(H^{+}) [/tex]

Hence, a solution with a pH of 7 is neutral. Also, a solution with a pH below 7 is acidic but basic (alkaline) if it's pH is above 7.

A pH meter can be defined as a scientific instrument or device designed and developed for the measurement of the hydrogen-ion concentration in water-based solutions, in order to determine their level of acidity or alkanility.

When using a pH meter to take a measurement, you should keep it in a storage solution until it is needed. Also, a deionized water should be used to rinse the pH meter and gently pat dry.

Furthermore, the pH meter should be placed in a given sample solution and a reading of the measurement taken when the pH of the solution stabilizes.

Answer:

The correct answer is - The net force is zero.

Explanation:

When an object moves on the surface with the same or constant acceleration which means there is no gain or loss of the speed it shows that all the forces of the object are at a point of zero.

If there would be any force applied on the object there must be some change in the velocity or acceleration but in this case there is no loss or gain of speed which means there is the object's net force is zero.

Therefore, option B is correct.

Answer:

false

Explanation:

False, water is a polyatomic molecule made up of two atoms of oxygen and 1 atom of hydrogen.

Explanation:

So, from this, we can conclude that water is a polyatomic molecule made up of two atoms of oxygen and 1 atom of hydrogen.

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Answer:

See Explanation

Explanation:

Rate of reaction refers to how quickly or slowly a reaction proceeds. The rate of reaction depends on certain factors.

Two among the factors that affect the rate of reaction are the concentration of reactants and the surface area of reactants.

The more the concentration of reactants, the faster the rate of reactants because there is a high possibility of collision between reactants. Also, the higher the surface area of reactants, the greater the rate of reaction.

In flour mills and coal mines where there is a large amount (concentration) of combustible materials and the particles are powdered (high surface area), there is a greater risk of explosion due to a high rate of reaction owing to a combination of the two factors discussed above.

Answer:

Hence,  

1) removed  

2) drained through the stopcock  

3) get eye level with  

4) slow the draining  

5) switch to a new flask

Explanation:

After mixing the solutions in a separatory funnel, the stopper should be removed and the liquid should be drained through the stopcock, and the layers allowed to separate. When you get close to the interface between the layers, get eye level with the funnel and turn over to slow the draining heat up until the first layer is collected. Switch to a new flask get eye level with it to collect the second layer.

Answer:

1.62 g

Explanation:

Given that:

Concentration of HCN = 0.119 M

Assuming the ka 4.00 × 10⁻¹⁰

The pKa of  HCN (hydrocyanic acid)  = -log (Ka)

= - log ( 4.00 × 10⁻¹⁰)

= 9.398

pH of buffer = 8.809

Using Henderson Hasselbach equation:

[tex]pH = pKa + log \dfrac{[conjugate\ base ]}{acid}[/tex]

[tex]pH = pKa + log \dfrac{[CN^-]}{[HCN]}[/tex]

[tex]8.809 = 9.398 +log \dfrac{[CN^-]}{[HCN]}[/tex]

[tex]log \dfrac{[CN^-]}{[HCN]}= 8.809 - 9.398[/tex]

[tex]log \dfrac{[CN^-]}{[HCN]}= -0.589[/tex]

[tex]\dfrac{[CN^-]}{[HCN]}= 0.2576[/tex]

[CN^-] = 0.2576[HCN]

[CN^-] = 0.2756 (0.119) L

[CN^-] = 0.033 M

∴

The amount of NaCN (sodium cyanide) is calculated as follows:

[tex]= 1.00 L \times \dfrac{0.033 \ mol \ NacN }{1 \ L } \times \dfrac{49.01 \ g}{1 \ mol \ of \ NacN}[/tex]

= 1.62 g

Answer:

Correct answer:

The equilibrium expression is defined as the ratio of the concentration of products divided by the concentration of the reactants. Each reactant or product is raised to the power corresponding to its coefficient in the balanced chemical equation.

Explanation:

Answer:

D

Explanation:

8oz=1cup

Xoz=1/4cup

cross multiply

Xoz=8×1/4=2

2oz=1/4cup

1oz=2T

2oz=x

cross multiply

×=2×2=4T

The cup of butter, number of tablespoons and ounces of butter are all in direct proportion with one another. The interpretation of the information provided is:

(b). The information provided gives the conversion factor 8oz/1 cup.

Given that:

[tex]1\ recipe = \frac{1}{4}\ cup[/tex]

[tex]1\ oz = 2T[/tex]

[tex]8\ oz = 1\ cup[/tex]

Multiply both sides of [tex]1\ oz = 2T[/tex] by 8

[tex]8 \times 1oz = 8 \times 2T[/tex]

[tex]8 oz = 16T[/tex]

Substitute 8oz for 1 cup in: [tex]1\ recipe = \frac{1}{4}\ cup[/tex]

[tex]1\ recipe = \frac{1}{4} \times 8oz[/tex]

Substitute [tex]8 oz = 16T[/tex]

[tex]1\ recipe = \frac{1}{4} \times 16T[/tex]

[tex]1\ recipe = 4T[/tex]

The interpretations are as follows:

Hence, (b) is correct

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Molecule is the general term used to describe any atoms that are connected by chemical bonds. Every combination of atoms is a molecule. A compound is a molecule made of atoms from different elements. All compounds are molecules, but not all molecules are compounds.

One example of a molecule is [tex]Cl_2[/tex] (chlorine).

Examples of a compound is NaCl (sodium chloride) or [tex]H_2O\\[/tex] (water)

Answer:

A new fictitious element was discovered.

It is a metal named jolmium, J, and it has three valence electrons.

If it combines with iodine it forms jolmium iodide. Answer the following questions.

a.Is this compound ionic or covalent

b. What is the formula of Jolmium iodide?

c. What is the charge on the metal J in this compound?

d. Explain how you know that is the charge?

Explanation:

It is given the element jolmium J is a metal with three valence electrons.

Since metals are highly electropositive, they lose electrons easily and form cations (Ions with a positive charge).

[tex]J^{3+}[/tex] ion will be formed.

b) The formula of jolmium iodide is shown below:

[tex]J^{+3} I^{-1}\\The formula becomes:\\JI_{3}[/tex]

a) The compound is ionic in nature.

Since the compound formed between a metal atom and a nonmetal atom will take place by transfer of electrons.

Hence, it is ionic in nature.

c) The charge on the metal J in this compound is +3.

d) Given J has three valence electrons.

That means it can lose three electrons to form a bond.

So, its valency is three.

Answer:

The answer is consumers

Answer:

Consumers are the group of organisms that has the least biomass and energy.

Answer:

atomic number

Explanation:

The mass number (A) of an element is obtained by summing the number of neutrons and protons (nucleons) in the atom of that element. However, the proton number of an element is its atomic number (Z). Hence, it can be said that:

mass number = no. of neutrons + atomic number/number of protons.

According to this question, an isotope of oxygen is said to have a mass number of 17. If the neutron number of this isotope is given as 9, then this means that its ATOMIC NUMBER or no. of protons of that isotope is (17 - 9) = 8.

Answer:

atomic number

Explanation:

Answer:

C. [tex]H_2S\rightarrow S+2H^++2e^-[/tex]

Explanation:

Hello there!

In this case, according to the given chemical reaction, it turns out possible to realize there is one sulfur atom on each side of the chemical equation but two hydrogen atoms on the left and one on the right, which means the latter must be balanced in agreement to the law of conservation of mass.

In such a way, by setting a 2 on H⁺, the reaction will be balanced:

[tex]H_2S\rightarrow S+2H^+[/tex]

Now, we count the transfer electrons for sulfur from -2 to 0 as 2e⁻ on the right, which will match with the option C.

[tex]H_2S\rightarrow S+2H^++2e^-[/tex]

Regards!

Explanation:

While the sun is an excellent source of energy, not all forms of life can utilize the sun's energy directly. This lesson describes how plants transform the sun's energy into potential energy stored in sugar, how living organisms utilize energy in sugar to perform work, and how the relationship between photosynthesis and cellular respiration is necessary for life.

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Answer:

Ka = [H⁺] × [CN⁻] / [HCN]

Explanation:

Cyanhydric acid is a weak acid, according to the following equation:

HCN(aq) ⇄ H⁺(aq) + CN⁻(aq)

The acid ionization constant (Ka) is equal to the product of the concentrations of the ions raised to the stoichiometric coefficients divided by the concentration of the undissociated acid raised to its stoichiometric coefficient.

Ka for HCN is:

Ka = [H⁺] × [CN⁻] / [HCN]

Answer:

.04 cg/L

Explanation:

Answer:

2.42x10⁹ years is the age of the rock

Explanation:

The decay of an isotope follows the equation:

Ln[A] = -kt + Ln[A]₀

Where [A] is amount of isotope after time t, k is decay constant and [A]₀ is the initial amount of the isotope

To find decay constant from half-life:

k = ln2 / half-life

k = ln2 / 1.26x10⁹years

k = 5.501x10⁻¹⁰ years⁻¹

As in the reaction, K-40 produce Ar-40:

[A] = 0.359mmol

[A]₀ = 0.359mmol + 1.000mmol = 1.359mmol

Replacing:

Ln[0.359mmol] = -5.501x10⁻¹⁰ years⁻¹t + Ln[1.359mmol]

-1.3312 = -5.501x10⁻¹⁰ years⁻¹t

t = 2.42x10⁹ years is the age of the rock

Answer: The correct option is A,

--> a.) Transition metals have partially filled d subshells.

Explanation:

Transition elements are all metals of economic importance. They are found in the d- lock of the periodic table between group 2 and 3. They occupy three rows, with ten elements in each row. The term 'transition metals' refers only to an element which has PARTIALLY filled d orbitals. Typical example of transition metals include iron (Fe).

They have partially filled 3d orbitals which are responsible for the special properties of the metals. These include:

--> Physical properties: the transition metals have high boiling and melting points. They are hard, dense and lustrous. They are also good conductors of heat and electricity.

--> Chemical reactivity: In the s- block and p-block, the chemical properties of the elements in the same period vary, often quite markedly, from left to right. This does not happen with the transition metals because electrons are added progressively to the inner d-orbitals.

--> Variable oxidation states: they have variable oxidation states because 3d electrons are available for bond formation.

Explanation:

Answer

Open in answr app

Correct option is

C

148

1 atom of Mg=1x24=24

2 atom of N=2x14=28

6 atom of O=6x16=96

Total mass=148

Answer:

At is a metalloid

Explanation:  Meaning that it displays some of the characteristics of a metal but can also display characteristics of nonmetals.  Silicon is one such element.  Elemental Silicon has a dark lustrous metallic appearance but it is quite brittle.  Some authorities include Astatine as a halogen as it has seven electrons in its valence shell placing it just below iodine in period 17 VIIA.  Additionally, because Astatine is only ever found naturally as the result of radioactive decay from more dense elements it is the rarest naturally occurring element in Earth's crust.

I hope this helps at least a little.

Regards,

JR Holt

Chemist retired  

Answer:

On the periodic table,periods are horizontal rows (across) the periodic table while groups are vertical columns (down) the table.We have groups in the periodic table like transition metals,rare earth,alkali metals ,alkaline earth metals halogens and noble gases

Answer:

Horizontal row call period and vertical column called group!

Physical,chemical, reaction procedure, shape,size, enthalpy of dissociation, bonding,non bonding, various things that segregated group and period....