round off each of the following numbers to two significant figure 0.436 and 9.000

Answer: 1

Explanation: Lithium has a single electron in the second principal energy level, and so we say that lithium has one valence electron.

1 is correct

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The balanced redox reaction in the chemical reaction is given below:

40H2S + 48H+ + 16MnO4¯ ---> 5S8 + 16Mn2+ + 64H2O

Balancing the redox reaction:

Solution:

1) Half-reactions:

H2S ---> S8

MnO4¯ ---> Mn2+

2) Balance:

8H2S ---> S8 + 16H+ + 16e¯

5e¯ + 8H+ + MnO4¯ ---> Mn2+ + 4H2O

3) Make the number of electrons equal (note that there are no common factors between 5 and 16 except 1):

40H2S ---> 5S8 + 80H+ + 80e¯ <--- factor of 5

80e¯ + 128H+ + 16MnO4¯ ---> 16Mn2+ + 64H2O <---

factor of 16

4) Thus, the final answer is given below;

40H2S + 48H+ + 16MnO4¯ ---> 5S8 + 16Mn2+ + 64H2O

Oxidation-reduction can simply be defined as a special type of chemical reaction in which the oxidation states of the substrate change.

So therefore, the balanced redox reaction in the chemical reaction is given below:

40H2S + 48H+ + 16MnO4¯ ---> 5S8 + 16Mn2+ + 64H2O

Complete question:

Balance the following redox reaction:

MnO4¯ + H2S ---> Mn2+ + S8

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The reaction above is a spontaneous reaction

Cu^2+ + 2Br^- --> Cu + Br2

A spontaneous redox reaction is a special type of redox reaction which involves the release of energy where the electrons are transferred from from an anode to the cathode

General spontaneous redox reactions is found mostly in electrochemical cells

So therefore, the reaction above is a spontaneous reaction.

Cu^2+ + 2Br^- --> Cu + Br2

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The pH of a 0.0100 M sodium benzoate solution is determined as 8.09.

The pH of a solution is a measure of hydrogen (H+) ion concentration, which is, in turn, a measure of acidity of the solution.

pH is can also be determined from pOH of the solution as shown below;

pH = 14 - pOH

let the hydroxyl concentration, OH = x

x²/M = kb

x²/0.01 = 1.5 x 10⁻¹⁰

x² = 1.5 x 10⁻¹²

x = √(1.5 x 10⁻¹²)

x = 1.2247 x 10⁻⁶

pOH = - log(OH⁻)

pOH = -log( 1.2247 x 10⁻⁶)

pOH = 5.91

pH = 14 - 5.91

pH = 8.09

Thus, the pH of a 0.0100 M sodium benzoate solution is determined as 8.09.

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∆H for given reaction -847kJ

So

2 mol of Al releases 847KJ heat

4 mol Al releases

∆H=-1694KJ

It is given that the energy released during the reaction of 2 moles of Al metal is - 847 KJ. The n the heat energy released by 4 moles of Al will be - 1694 KJ.

The enthalpy change of a reaction is the heat energy absorbed or released by a reaction. For an endothermic reaction, the heat energy is absorbed and the enthalpy change is positive. For an exothermic reaction, where the energy is released, the enthalpy change will be negative.

The heat energy change during a reaction is equal to the product of mass, specific heat and temperature difference of the substanc eunder reaction or phase transition.

Given that, the heat evolved by 2 moles of Al is - 847 kJ. Then, the heat evolved when 4 moles of Al reacted is calculated as follows:

(4 × - 847) / 2 = - 1694 KJ.

Therefore, the heat energy released is  - 1694 KJ.

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The best effect of chemicals on the environment is that Chemicals can be helpful or harmful to the environment.

Environmental chemical compounds seek advice from a chemical compound or chemical element present in air, water, meals, soil, dust, or other environmental media which includes customer merchandise.

Chemical substances can be toxic due to the fact they are able to harm us after they enter or touch the frame. exposure to a poisonous substance together with fuel can have an effect on your fitness. due to the fact that drinking gas can motive burns, vomiting, diarrhea and, in very huge amounts, drowsiness or dying, it's far poisonous.

Nutrient loading from over-fertilization can bring about runoff that causes damaging consequences in aquatic ecosystems. sizable publicity to, or misuse of, insecticides can damage non-centered plants and animal, as well as lead to improvement of pesticide-resistant pest species.

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in the periodic tables

elements in the same column have the same charge

in a compound oxidation numbers have to equal 0

1.

sulfur in Li2SO3

charges :

Li = +1 S = +4 O = -2

multiply the charge with the subscripted number next to the element

Li = +1

Li2 = +2

O = -2

O3 = -8

in a compound oxidation numbers have to equal 0

+2 S -6 = 0

S -4 = 0

S = +4

Sulfur = +4

2.

MgCl2

Mg = +2

+2 Cl2 = 0

Cl2 = -2

Cl by itself = -2 divided by 2 = -1

Chlorine  = -1

3.

SiO2

Silicon = +4

4.

Sulfur in H2SO4

H: +1 S: +6 O: -2

H2SO4

H2 : +2 O4: -8

+2 +S -8 = 0

S - 6 = 0

S = +6

Sulfur = +6

5.

Sulfur in SO4^2-

Sulfur in SO4

Sulfur = +4

6.

Manganese in MnO4^-

Manganese in MnO4

Manganese = +4

7.

Cr2O7^2-

Dichromate

Cr in Cr2O7^2- or Cr2O7-2-

Cr: +6 O: -2

Answer:

52.07 L H₂

Explanation:

Before you can find the volume of H₂, you need to find the moles of H₂. To do this, you need to (1) convert grams Mg to moles (via the atomic mass) and then (2) convert moles Mg to moles H₂ (via the mole-to-mole ratio from equation coefficients).

Atomic Mass (Mg): 24.30 g/mol

1 Mg(s) + 2 HCl(aq) ---> MgCl₂(aq) + 1 H₂(g)
^                                                         ^

56.49 g Mg           1 mole               1 mole H₂
-------------------  x  -----------------  x  --------------------  =  2.32 moles H₂
                              24.30 g            1 mole Mg

Now that you know the moles of H₂, you need to determine the volume at STP. To do this, you need to set up a proportion comparing the mole value versus the volume. Then, you can cross-multiply to solve for the unknown volume. The final answer should have 4 sig figs to match the given values.

 1 mole            2.32 moles
--------------  =  --------------------                      <----- Set up proportion
  22.4 L                 ? L

(1 mole) x ? L = 52.07                                 <----- Cross-multiply

? L = 52.07                                                <----- Divide both sides by 1 mole

Answer:

[OH⁻] = 2.2 x 10⁻¹²

Explanation:

(Step 1)

Calculate the pH.

pH = -log[H⁺]

pH = -log[4.6 x 10⁻³]

pH = 2.34

(Step 2)

Find the pOH.

pH + pOH = 14

2.34 + pOH = 14

pOH = 11.66

(Step 3)

Calculate the [OH⁻].

[OH⁻] = 10^(-pOH)

[OH-] = 10^(-11.66)

[OH⁻] = 2.2 x 10⁻¹²

The amount of heat transferred from an object depends on the following;

The initial temperature of the object

The specific heat of the object

The mass of the object

Therefore, the answer is all of the above (option B).

What is heat?

Heat is the internal energy of a system in thermodynamic equilibrium due to its temperature.

The amount of heat absorbed or released by an object can be calculated using the following expression:

Q = m × c × ∆T

Where;

Q = quantity of heat

m = mass of object

c = specific heat capacity of object

∆T = change in temperature

Therefore, this suggests that amount of heat transferred from an object depends on the following;

The initial temperature of the object

The specific heat of the object

The mass of the object

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A. The heat is needed to melt 100.0 grams of ice that is already at 0°C is +33,400 J.

Specific heat capacity is the quantity of heat needed to raise the temperature per unit mass.

The heat is needed to melt 100.0 grams of ice that is already at 0°C is calculated as follows;

Q = mL

where;

Q = 100 x 334

Q = 33,400 J

Thus, the heat is needed to melt 100.0 grams of ice that is already at 0°C is +33,400 J.

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Taking into account the Henry's Law, 1.297 g carbon dioxide will dissolve at 790 mm Hg in 1.01 L water.

A change in pressure does not appreciably influence the solubility of solids or liquids or liquids in liquids; however, that of gases in solvents increases when the partial pressure of the gases increases. The solubility of a gas depends on pressure and temperature.

In this way, Henry's Law describes the effect of pressure on the solubility of gases. This law states that the solubility of a gas in contact with the surface of a liquid at a given temperature is directly proportional to the partial pressure of said gas on the liquid.

Mathematically, Henry's law is expressed as:

C=k×P

Where:

At 2 different partial pressure values, the Henry's law is expressed as:

[tex]\frac{C1}{C2} =\frac{P1}{P2}[/tex]

In this case, you know:

Replacing in Henry's Law:

[tex]\frac{1.228\frac{g}{L} }{C2} =\frac{755 mmHg}{790mmHg}[/tex]

Solving:

[tex]1.228\frac{g}{L} =\frac{755 mmHg}{790mmHg}xC2[/tex]

C2= [tex]\frac{1.228\frac{g}{L} }{\frac{755 mmHg}{790mmHg}}[/tex]

C2= 1.285 [tex]\frac{g}{L}[/tex]

Then, the concentration of carbon dioxide at 790 mmHg is 1.285 g/L. But you have 1.01 L of water. So the amount of gas dissolved can be calculated as 1.01 L×1.285 g/L = 1.297 g

Finally, 1.297 g carbon dioxide will dissolve at 790 mm Hg in 1.01 L water.

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Answer: Lithium - 8

Answer:

Lithium-8

Explanation:

The atom with three protons and five neutrons that has a mass number of eight is known as lithium-8.

Answer:

B.) 129.9 grams

Explanation:

To find the mass, you need to use the following equation:

Q = mcΔT

In this equation,

-----> Q = energy (J)

-----> m = mass (g)

-----> c = specific heat (J/g°C)

-----> ΔT = change in temperature (°C)

The specific heat of copper is 0.385 J/g°C. Knowing this, you can plug the given values into the equation and simplify to isolate "m".

Q = mcΔT                                                            <----- Equation

5000 J = m(0.385 J/g°C)(200 °C - 100 °C)        <----- Insert values

5000 J = m(0.385 J/g°C)(100)                            <----- Subtract

5000 J = m(38.5)                                                <----- Multiply 0.385 and 100

129.9 = m                                                             <----- Divide both sides by 38.5

Answer:

C

Explanation:

Of course increasing the pressure will reduce the volume

P1V1 = P2V2

P1V1/P2 = V2     WHEN P2 = 2 P1----multiply both sides by 1/2

P1 V1 / 2P1 = 1/2 V2    <===== 1/2 the original

Answer:

Explanation:

The term you want is the critical mass. It is the mass needed to trigger a nuclear reaction and keep it going.

Approximately 104 pounds of Uranium 235 is needed for the critical mass to occur. If it is less than 104 pounds, no reaction will occur.

Answer:

9.89 x 10²³ molecules H₂S

Explanation:

To find the molecules of H₂S, you need to (1) convert grams S to moles S (via the atomic mass of sulfur), then (2) convert moles S to moles H₂S (via the mole-to-mole ratio from equation coefficients), and then (3) convert moles H₂S to molecules H₂S (via Avogadro's Number). It is important to arrange the ratios/conversions in a way that allows for the cancellation of units. The final answer should have 3 sig figs to match the sig figs of the given value.

Atomic Mass (S): 32.065 g/mol

2 H₂S(s) + SO₂(g) -----> 3 S(s) + 2 H₂O(l)

Avogadro's Number:

6.022 x 10²³ molecules = 1 mole

79.0 g S           1 mole            2 moles H₂S          6.022 x 10²³ molecules
---------------  x  ---------------  x  ----------------------  x  -------------------------------------  =
                        32.065 g            3 moles S                          1 mole

=  9.89 x 10²³ molecules H₂S

Answer:

B.) The reaction will shift to the right to produce more product.

Explanation:

When the pressure of a reaction is increased, the equilibrium shifts to the side with less moles of gas.

You can determine the moles of gas by adding the coefficients on each side of the reaction. The reactants have 4 moles of gas (1 + 3 = 4) and the products have 2 moles of gas. Since there are less moles of gas on the product side, the equilibrium will shift to that side. As such, more product will be produced.

Answer:

d

Explanation:

d

Answer:

B.) [tex]K_{eq} = \frac{[SO_3][NO]}{[SO_2][NO_2]}[/tex]

Explanation:

The general equilibrium expression looks like this:

[tex]K_{eq} = \frac{[C]^c[D]^d}{[A]^a[B]^b}[/tex]

In this expression,

-----> K = equilibrium constant

-----> uppercase letters = formulas

-----> lowercase letters = balanced equation coefficients

The products are in the numerator and the reactants are in the denominator. Since all of the molecules are gases, they should all be included in the expression. Since the coefficients in the balanced equation are all 1, they do not need to be represented in the expression.

The equilibrium constant expression is:

[tex]K_{eq} = \frac{[SO_3][NO]}{[SO_2][NO_2]}[/tex]

Answer:

See below

Explanation:

45 kJ / gm   * .77  gm / liter  * 13 liter =  _________  kJ

Burning 13 L of gasoline would produce 450,450 kJ of energy. For calculating the amount of energy produced by burning 13 L of gasoline, we can use the given information that 1 gram of gasoline produces 45.0 kJ of energy when burned and the density of gasoline is 0.77 g/mL.

First, we need to convert the volume of gasoline from liters to milliliters since the density is given in grams per milliliter.

13 L = 13,000 mL

Next, we can calculate the mass of the gasoline using the density:

Mass = Volume x Density

Mass = 13,000 mL x 0.77 g/mL

Mass = 10,010 g

Now, we can calculate the amount of energy produced by multiplying the mass of gasoline by the energy produced per gram:

Energy = Mass x Energy per gram

Energy = 10,010 g x 45.0 kJ/g

Energy = 450,450 kJ

Therefore, burning 13 L of gasoline would produce 450,450 kJ of energy.

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Excess water and impurities. Option A.

In the actual sense of it, no chemical reaction can give over a 100% yield. The upper limit cannot be breached. Thus, if more than a 100% yield is obtained, there is a problem somewhere.

One of the problems could be that the product is not sufficiently dried. In other words, excess water has contributed to the yield of the reaction.

The second likely problem could be that at some points during the reaction, impurities have been introduced. The weight of the impurities will add to the actual yield and give a bogus over a 100% yield.

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B. At the equivalence point of a titration of the [H+] concentration is equal to 7.

The equivalence point of a titration is a point in titration at which the amount of titrant added is just enough to completely neutralize the analyte solution.

At the equivalence point in an acid-base titration, moles of base equals moles of acid and the solution only contains salt and water.

At the equivalence point, equal amounts of H+ and OH- ions combines as shown below;

H⁺ + OH⁻  → H₂O

The pH of resulting solution is 7.0 (neutral).

Thus, the pH at the equivalence point for this titration will always be 7.0.

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The statement that is a part of Kinetic Molecular Theory (KMT) is Molecules in a gas move rapidly. That is option B.

Kinetic Molecular Theory (KMT) is defined as the theory that describes the physical behaviour of gases.

The Kinetic Molecular Theory (KMT) include the following:

Therefore, the statement that is a part of Kinetic Molecular Theory (KMT) is Molecules in a gas move rapidly.

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When the crystals of potassium permanganate are preserved in water, the purple-coloured crystals of potassium permanganate break further into smaller particles that populate the distance between the molecules of water imparting a purple colour to the water. This is an example of diffusion.

Diffusion is the process of movement of solvent from higher concentration to lower concentration through a semipermeable membrane. So, we can form the decision that it cannot occur through a thick membrane from which small molecules cannot pass through.

Osmosis is the direction of solvent particles from a solution that is diluted to a more concentrated one. In contrast, diffusion is the movement of particles from a higher concentration region to a part of lower concentration.

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A. The balanced chemical reaction of Sodium metal and Water is 2Na  +  2H₂O  →  2NaOH    +   H₂.

A balanced equation contains the same number of each type of atoms on both the left and right sides of the reaction arrow.

Sodium metal reacts rapidly with water to form a colourless solution of sodium hydroxide (NaOH) and hydrogen gas (H2).

The balanced chemical reaction is written below;

2Na  +  2H₂O  →  2NaOH    +   H₂

Thus, the balanced chemical reaction of Sodium metal and Water is 2Na  +  2H₂O  →  2NaOH    +   H₂.

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