The number of moles of aluminum that react with 15.7 grams of oxygen according to the equation 4 Al + 3 0 2 - 2 Al 20 3

Answer: There are [tex]1.23 \times 10^{22}[/tex] atoms present in 37.1 mg of tantalum.

Explanation:

Given: Mass of single tantalum atom = [tex]3.01 \times 10^{-22} g[/tex]

Mass of tantalum atoms = 37.1 mg (1 mg = 0.001 g) = 0.0371 g

Therefore, number of tantalum atoms present in 0.0371 grams is calculated as follows.

[tex]No. of atoms = \frac{0.0371 g}{3.01 \times 10^{-22}}\\= 1.23 \times 10^{20}[/tex]

Thus, we can conclude that there are [tex]1.23 \times 10^{22}[/tex] atoms present in 37.1 mg of tantalum.

There are [tex]1.23\times 10^{20}[/tex] atoms of tantalum in 37.1 mg of tantalum.

Explanation:

Given:

Mass of single atom of tantalum =[tex]3.01\times 10^{-22} g[/tex]

To find:

The number of atoms of tantalum in 37.1 milligrams.

Solution:

Mass of tantalum = 37.1 mg

[tex]1 mg = 0.001 g\\37.1 mg=37.1\times 0.001 g=0.0371 g[/tex]

The number of atoms in 0.0371 grams of tantalum = N

Mass of a single atom of tantalum = [tex]3.01\times 10^{-22} g[/tex]

Then a mass of N atoms of tantalum will be:

[tex]0.0371 g=N\times 3.01\times 10^{-22} g\\N=\frac{0.0371 g}{ 3.01\times 10^{-22} g}\\=1.23\times 10^{20}[/tex]

There are [tex]1.23\times 10^{20}[/tex] atoms of tantalum in 37.1 mg of tantalum.

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Answer:

34.03 g

Explanation:

We'll begin by converting 635 mL to L. This can be obtained as follow:

1000 mL = 1 L

Therefore,

635 mL = 635 mL × 1 L / 1000 mL

635 mL = 0.635 L

Thus, 635 mL is equivalent to 0.635 L

Next, we shall determine the number of mole of the solute (KBr) in the solution. This can be obtained as follow:

Volume = 0.635 L

Molarity = 0.450 M

Mole of KBr =?

Mole = Molarity × Volume

Mole of KBr = 0.450 × 0.635

Mole of KBr = 0.286 mole

Finally, we shall determine the mass of 0.286 mole of KBr. This can be obtained as follow:

Mole of KBr = 0.286 mole

Molar mass of KBr = 39 + 80

= 119 g/mol

Mass of KBr =?

Mass = mole × molar mass

Mass of KBr = 0.286 × 119

Mass of KBr = 34.03 g

Thus, the mass of the solute (KBr) in the solution is 34.03 g

Answer:

a. 8.3= pKa of the aminoacid

b. Cysteine

Explanation:

The pH of an acid can be obtained using the H-H equation:

pH = pKa + log [A-] / [HA]

Where pH is the pH of the buffer = 7.0

pKa is the pka of the conjugate acid = ?

[A-] / [HA] is the ratio between conjugate base and conjugate acid. As the ratio of conjugate acid to conjugate base = 20:1, the [A-] / [HA] = 1/20

Replacing:

7 = pKa + log 1/20

7 = pKa - 1.30

7+1.30 = 8.3 = pKa of the aminoacid

The only aminoacid with a side chain with pKa = 8.3 is:

Cysteine. Allowing its identification.

Explanation: The hypothesis is a prediction, but it involves more than a guess. Most of the time, the hypothesis begins with a question which is then explored through background research. It is only at this point that researchers begin to develop a testable hypothesis.

(Unless you are creating an exploratory study, your hypothesis should always explain what you expect to happen)

Answer:

3.65 g of cyclohexene

Explanation:

Cyclohexanol + phosphoric acid ----> cyclohexene

The reaction is 1:1 hence the limiting reactant is phosphoric acid.

Hence,

1 mole of phosphoric acid yields 1 mole of cyclohexene

0.0444 moles of phosphoric acid yields 0.0444 moles of cyclohexene

Theoretical yield = number of moles of cyclohexene × molar mass of cyclohexene

Theoretical yield = 0.0444 moles of cyclohexene × 82.143 g/mol

Theoretical yield = 3.65 g of cyclohexene

Answer:

1 ) Δs ( entropy change for hot block ) = - Q / th  ( -ve shows heat lost to cold block )

Δs ( entropy change for cold block ) = Q / tc

∴ Total Δs = ΔSc + ΔSh

                 = Q/tc - Q/th

2) ΔSdecomposition = Δh / Temp = ( 181.6 * 10^3 / 773 ) = 234.928 J/k

Explanation:

1) To show that heat flows spontaneously from high temperature to low temperature

example :

Pick two(2) solid metal blocks with varying temperatures ( i.e. one solid block is hot and the other solid block is cold )

Place both blocks for time (t ) in an insulated system to reduce heat loss or gain to or from the environment

Check the temperature of both blocks after time ( t ) it will be observed that both blocks will have same temperature after time t ( first law of thermodynamics )

Δs ( entropy change for hot block ) = - Q / th  ( -ve shows heat lost to cold block )

Δs ( entropy change for cold block ) = Q / tc

∴ Total Δs = ΔSc + ΔSh

                 = Q/tc - Q/th

2) Entropy change for Decomposition of mercuric oxide

2HgO (s) → 2Hg(l) + O₂ (g)

Δs = positive

there is transition from solid to liquid and the melting point of mercury ( the point at which reaction will take place ) = 500⁰C

hence ΔSdecomposition = S⁻ Hg  -  S⁻ HgO =

Δh of reaction = 181.6 KJ

Temp = 500 + 273 = 773 k

hence ΔSdecomposition = Δh / Temp = ( 181.6 * 10^3 / 773 ) = 234.928 J/k

Answer:

Explanation:

The mechanism of the reaction is shown in the diagram below. From the reaction, when (2S,3S)-2-Bromo-3-phenylbutane undergoes a reaction with sodium ethoxide (ETONa), the E2 elimination reaction is put into place. Here, the H and the leaving group are antiperiplanar to one another and the reaction mechanism proceeds to form an isomeric (E)-2-phenyl-2butane as the major product.

Answer:

H2

Explanation:

Answer:

[tex]{ \bf{H _{2} }} \\ { \tt{hydrogen \: gas}}[/tex]

Answer:

Earth has a mass of 5.9736×1024 kg

hope it is helpful to you

Answer:

For (1): The correct option is (a)

For (2): The correct option is (a) and 333.6 kJ of heat will be absorbed when 70.9 g of ammonia reacts.

Explanation:

There are 2 types of reactions that are classified based on enthalpy change:

Endothermic reactions: These are the reactions where heat is absorbed by the reaction. The change in enthalpy of the reaction, [tex]\Delta H_{rxn}[/tex] is positive for these reactions.

Exothermic reactions: These are the reactions where heat is released by the reaction. The change in enthalpy of the reaction, [tex]\Delta H_{rxn}[/tex] is negative for these reactions.

For the given chemical reaction:

[tex]2NH_3(g)\rightarrow N_2(g)+3H_2(g);Delta H=160kJ[/tex]

As the change in enthalpy or heat of the reaction is positive. Thus, the reaction is an endothermic reaction because heat is absorbed by the reaction.

When ammonia reacts, some amount of heat will be absorbed by the reaction. Thus, we can say the heat will be absorbed.

The number of moles is calculated by using the equation:

[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] ......(1)

Given mass of ammonia = 70.9 g

Molar mass of ammonia = 17 g/mol

Using equation 1:

[tex]\text{Moles of ammonia}=\frac{70.9g}{17g/mol}=4.17mol[/tex]

By stoichiometry of the reaction:

If 2 mole of ammonia reacts, the heat absorbed is 160 kJ

So, if 4.17 moles of ammonia reacts, the heat absorbed will be = [tex]\frac{160kJ}{2mol}\times 4.17mol=333.6kJ[/tex]

Hence, 333.6 kJ of heat will be absorbed when 70.9 g of ammonia reacts

Answer: A mass of 0.518 g of phenol must be dissolved in 25.0 g of naphthalene to produce a solution that is 0.22 m in phenol.

Explanation:

Given: Mass of naphthalene = 25.0 g

Molality = 0.22 m

This means that 0.22 moles of solute is present per kg of solvent.

As 25.0 g  of naphthalene is there that will be 25.0 g per 1000 g (1 kg) is equal to 0.025 kg.

Hence, moles of phenol are calculated as follows.

[tex]Molality = \frac{moles}{mass (in kg)}\\0.22 m = \frac{moles}{0.025 kg}\\moles = 0.0055 mol[/tex]

Also, molar mass of phenol is 94.11 g/mol. This means that 1 mole of phenol contains 94.11 g.

Therefore, mass contained by 0.0055 moles of phenol is as follows.

[tex]0.0055 mol \times 94.11 g/mol \\= 0.518 g[/tex]

Thus, we can conclude that a mass of 0.518 g of phenol must be dissolved in 25.0 g of naphthalene to produce a solution that is 0.22 m in phenol.

Answer:

To transfer leftover solids to the filtration funnel and wash out crystals after recrystallization, ice cold methanol should be used (the mother liquor used for recrystallization).

Explanation:

Hope this helped

Answer: the answer is A

Explanation: add me hope i helped

Answer:

7.6×10¹⁰

Explanation:

7.296×10²÷9.6×10⁻⁹

To solve such problem,

We group the whole number ans solved seperately and also group the indices and solve the seperately

Step1 : 7.296/9.6 = 0.76

Step 2: applying the law of indices,

10²÷10⁻⁹ = 10⁽²⁺⁹⁾ = 10¹¹

Therefore,

7.296×10²÷9.6×10⁻⁹ = 0.76×10¹¹ = 7.6×10¹⁰

Answer: If matter goes through a chemical change then the physical properties are not likely to stay the same.

Explanation:

When chemical composition of a substance changes during a chemical reaction then it is called a chemical change.

Chemical change always leads to the formation of new substances. Properties like chemical reactivity, combustion, rusting etc are chemical changes.

For example, [tex]N_{2} + 3H_{2} \rightarrow 2NH_{3}[/tex]

Here, [tex]NH_{3}[/tex] will have different chemical as well as physical properties as compared to [tex]N_{2}[/tex] and [tex]H_{2}[/tex].

As physical properties are the properties that cause change in state of a substance.

Properties like boiling point, state of substance etc are physical properties.

Thus, we can conclude that if matter goes through a chemical change then the physical properties are not likely to stay the same.

Answer:

Active transport by the Na+-K+ pump

Explanation:

Active transport by the Na+-K+ pump

Maintenance (and restoration) of the resting ion concentrations depends on the Na+-K+ pump. Once gated ion channels are closed, the combined action of the pump and ion leakage (particularly that of K+) establishes a resting membrane potential in a typical neuron of around âˆ'70 mV.

Answer: The statement it is endothermic because the energy required to break bonds in the reactants is less than the energy released when the products are formed, is true.

Explanation:

A chemical reaction in which heat energy  is released is called an exothermic reaction. For exothermic reactions, the value of [tex]\Delta H[/tex] is always negative.

A chemical reaction in which heat energy is absorbed is called an endothermic reaction. For endothermic reaction, the value of [tex]\Delta H[/tex] is always positive.

In endothermic reactions, energy required for breaking the bonds between reactants is less than the energy when products are formed due to which the value of [tex]\Delta H[/tex] remains positive.

Thus, we can conclude that the statement it is endothermic because the energy required to break bonds in the reactants is less than the energy released when the products are formed, is true.

It is endothermic because the energy required to break bonds in the reactants is greater than the energy released when the products are formed. The correct option is B.

The above reaction is endothermic because more energy is produced when new bonds form in the products (H = 920 kJ/mol) than is required to break bonds in the reactants (H = -750 kJ/mol).

In an endothermic process, more energy than is generated during bond creation is absorbed from the environment to dissolve existing bonds. This causes a net absorption of energy, which cools the system.

The reaction takes more energy than it releases, proving its endothermic nature, as seen by the positive difference between the energy needed to dissolve bonds and the energy released during bond formation.

Thus, the correct option is B.

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Your question seems incomplete, the probable complete question is:

During a reaction, ΔH for reactants is −750 kJ/mol and ΔH for products is 920 kJ/mol. Which statement is correct about the reaction? (5 points)

Group of answer choices

A. It is endothermic because the energy required to break bonds in the reactants is less than the energy released when the products are formed.

B. It is endothermic because the energy required to break bonds in the reactants is greater than the energy released when the products are formed.

C. It is exothermic because the energy required to break bonds in the reactants is less than the energy released when the products are formed.

D. It is exothermic because the energy required to break bonds in the reactants is greater than the energy released when the products are formed.

The question is incomplete, the complete question is;

What functional group results when cyclopentanone reacts with ethylamine in the presence of trace acid? A) cyanohydrin B) semicarbazone C) imine D) enamine E) oxime

Answer:

imine

Explanation:

An imine is an unsaturated amine. An imine contains the carbon- nitrogen double bond.

Imines are obtained when a carbonyl compound is condensed with NH3 or an amine. The reaction involves several steps in its mechanism.

Since cyclopentanone is a ketone (carbonyl compound) and ethylamine is an amine,in the presence of trace acid, condensation of the two compounds occur to yield an imine

Answer:

hope it helps much as you can

Answer:

Organic fertilizers are those fertilizers that are not artificially produced but are natural and has carbon in them.

Fertilizers in the broad term are used to provide nutrient to the soil and boost growth of crops.

Some of the advantages of organic fertilizers to inorganic fertilizers are:

They do not make crusts on the soil, unlike inorganic fertilizers.

They help add structure to the soil because of the good water movement into the soil

They are easier on the soil because they feed good microbes.

Explanation:

hope the picture above helps you to understand:)

Answer:

6.7855 * 10^18

Explanation:

There are 2 moles in H2

Avagadro's number: 6.022E23

8.14E42*1/6.022E23 * 1/2

=6.7855 * 10^18

Answer:

There will be very little of BrOCl BrCl

Explanation:

Based on the equilibrium:

Br2(g) + OCl2(g) ⇄ BrOCl(g) + BrCl(g)

The equilibrium constant, Kc, is:

Kc = 1.58x10⁻⁵ = [BrOCl] [BrCl] / [Br2] [OCl2]

As Kc is <<< 1, in equilibrium, the concentration of products will remain lower regard to the concentration of the reactants. That means, right answer is;

Answer:

light energy is converted to chemical energy during photosynthesis.

Explanation:

Law of conservation of energy says: Energy can neither be created nor destroyed-only converted from one form of energy to another.

Answer:

Answer: The property of all bases is that they are substances which neutralizes an acid to form a salt and water only.

Explanation:

A base is also s substance that can accept or combine with a proton; a proton acceptor.

Bases include the oxides, hydroxides and carbonates of metals. These include MgO,Na2O, NaOH,Ca(OH)2. Most metals burn in oxygen to form metallic oxides which are basic. Examples are the MgO and Na2O.

Other properties or characteristics of bases includes:

--> They have a bitter taste.

--> They turn red litmus paper blue.

--> They are soapy to touch.

--> Aqueous solutions of bases are also electrolytes. Bases can be either strong or weak, just as acids can.

Bases (sodium hydroxide) can be used in the preparation of soaps, glass, paper and rayon. While some bases (magnesium hydroxide) can also be used to manufacture toothpaste and laxatives.

Answer: The balanced half-equations for silver + oxygen= silver oxide are:

Oxidation-half reaction: [tex]Ag \rightarrow 2Ag^{+} + 2e^{-}[/tex]

Reduction-half reaction: [tex]O_{2} + 2e^{-} \rightarrow 2O^{-}[/tex]

Explanation:

The word equation is as follows.

silver + oxygen = silver oxide

In terms of chemical formulas this equation can be written as follows.

[tex]Ag + O_{2} \rightarrow Ag_{2}O[/tex]

The removal on electron(s) from an atom, ion or molecule in a chemical reaction is called oxidation.

The gain of electron(s) by an atom, ion or molecule in a chemical reaction is called reduction.

Hence, half-reaction equations for the given reaction is as follows.

Oxidation-half reaction: [tex]Ag \rightarrow 2Ag^{+} + 2e^{-}[/tex]

Reduction-half reaction: [tex]O_{2} + 2e^{-} \rightarrow 2O^{-}[/tex]

As the number of atoms participating in the reaction are equal. Hence, the half-equations are balanced.

Thus, we can conclude that the balanced half-equations for silver + oxygen = silver oxide are:

Oxidation-half reaction: [tex]Ag \rightarrow 2Ag^{+} + 2e^{-}[/tex]

Reduction-half reaction: [tex]O_{2} + 2e^{-} \rightarrow 2O^{-}[/tex]

Answer:

a. minus 10

Explanation:

An element in group 13 = Boron ,valence electrons = 3 , therefore, valence electrons in group 13 = group no. -10

An element in group 18 = Neon, valence electrons = 8 , therefore, valence electrons in group 18 = group no. - 10

For groups 13 through 18, the number of valence electrons in an atom is equal to the group number minus 10. Therefore, option (A) is correct.

Valence electrons in an atom can be described as the electrons occupying the outer most electron shell of an atom while the electrons in the inner shell are core electrons. Lewis structures can be helpful to calculate the number of valence electrons.

Valence electrons can be filled in several electron shells as they are caused interaction between atoms and responsible for the formation of chemical bonds. Only valence electrons can contribute to the formation of a chemical bond and decide the reactivity of the element.

The general electronic configuration of group 13 is ns²np¹ has three valence electrons. It can be determined as group number - 10 = 13 - 10 = 3.

The general electronic configuration of group 18 is ns²np⁶ has eight valence electrons. It can be determined as group number - 10 = 18 - 10 = 8.

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Answer:

0.1 L

Explanation:

From the question given above, the following data were obtained:

Concentration of stock solution (C₁) = 1.25 M

Volume of diluted solution (V₂) = 0.5 L

Concentration of diluted solution (C₂) = 0.25 M

Volume of stock solution needed solution (V₁) =?

The volume of the stock solution needed can be obtained as follow:

C₁V₁ = C₂V₂

1.25 × V₁ = 0.25 × 0.5

1.25 × V₁ = 0.125

Divide both side by 1.25

V₁ = 0.125 / 1.25

V₁ = 0.1 L

Therefore, the volume of the stock solution needed is 0.1 L