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Ivanshal [37]
3 years ago
6

If you need to reverse the following reaction in order for it to be an intermediate reaction in a Hess's law problem, what would

be the final value for the enthalpy of reaction you use for this intermediate reaction? H2 + 0.5 O2 H2O, H = -286 kJ
Chemistry
2 answers:
Olin [163]3 years ago
4 0
When reversing a given reaction, we simply change the sign of the standard enthalpy change value. Therefore, the reaction will become:
H₂O → H₂ + 0.5O₂, ΔH = 286kJ
This is because if a certain amount of energy is released when a reaction occurs, the same amount of energy must be supplied for the reaction to occur in the reverse direction.
castortr0y [4]3 years ago
3 0

Answer:

<u>286 KJ</u> is the answer

Explanation:

You might be interested in
How many liters of hydrogen gas will be produced at STP from the reaction of 7.179 x 1023 atoms of magnesium with 54.21 g of pho
wlad13 [49]
<h3>Answer:</h3>

18.58 liters of hydrogen gas

<h3>Explanation:</h3>

We are given;

  • The equation;

3Mg + 2H₃(PO₄) → Mg₃(PO₄)₂ + 3H₂

  • Atoms of Magnesium = 7.179 x 10^23 atoms
  • Mass of phosphoric acid as 54.21 g

We are required to determine the volume of hydrogen gas produced;

Step 1; moles of Magnesium

1 mole of an element contains 6.02 × 10^23 atoms

therefore;

Moles of Mg = (7.179 x 10^23 ) ÷ (6.02 × 10^23)

                   = 1.193 moles

Step 2: Moles of phosphoric acid

moles = Mass ÷ Molar mass

Molar mass of phosphoric acid = 97.994 g/mol

Therefore;

Moles of Phosphoric acid = 54.21 g ÷ 97.994 g/mol

                                           = 0.553 moles

Step 3: Determine the rate limiting reagent

From the mole ratio of Mg to Phosphoric acid (3 : 2);

1.193 moles of magnesium requires 0.795 moles of phosphoric acid while,

0.0553 moles of phosphoric acid requires 0.8295 moles of Mg

Therefore, phosphoric acid is the rate limiting reagent

step 4: Determine the moles of hydrogen produced

From the equation, w moles of phosphoric acid reacts to produce 3 moles of hydrogen;

Therefore; moles of Hydrogen = moles of phosphoric acid × 3/2

                                                   = 0.553 moles × 3/2

                                                   = 0.8295 moles

Step 5: Volume of hydrogen gas

1 mole of a gas occupies a volume of 22.4 liters at STP

Therefore;

Volume of Hydrogen = 0.8295 moles × 22.4 L/mol

                                  = 18.58 Liters

Therefore; 18.58 liters of hydrogen gas  will be produced

4 0
3 years ago
TIMED PLS HELP AND WILL GIVE BRAINLIST
Strike441 [17]

Answer:

19.4 g of alum, will be its theoretical yield

Explanation:

The reaction is:

2 Al + 2 KOH + 4 H₂SO₄ + 22H₂O → 3H₂ + 2KAl(SO₄)₂•12H₂O

Let's determine the amount of acid.

M are the moles contained in 1 L of solution or it can be mmoles that are contained in 1 mL of solution

M = mmol /mL

M . mL = mmol

We replace: 8.3 mL . 9.9 M = 82.17 mmoles

We convert to moles: 82.17 mmol . 1 mol / 1000mmol = 0.082 moles

Ratio is 4:2

4 moles of sulfuric acid can make 2 moles of alum

By the way, 0.082 moles of acid may produce ( 0.082 . 2) /4 = 0.041085 moles.

We convert moles to mass:

Molar mass of alum is: 473.52 g/mol.

0.041085 moles . 473.52 g/mol = 19.4 g

6 0
3 years ago
In Lab 10 you make a stock solution of salicylic acid, and then four dilutions. The stock solution is made by diluting 5.00 ml o
Zigmanuir [339]

Answer:

Stock  solution =  1.25 *10^-3 M

Dilution 1 = 5*10^-4 M

Dilution 2= 3.75 * 10^-4 M

Dilution 3 = 2.5 *10^-4 M

Dilution 4 = 1.25 *10^-4 M

Explanation:

<u>Step 1:</u> Data given

The stock solution is made by diluting 5.00 ml of 1.250 x 10-2 M salicylic acid in 50.00 mL of solution.

<u>Step 2</u>: Calculate the concentration of the stock solution:

M1*V1 = M2*V2

⇒ with M1 = the initial concentration = 1.250 *10^-2 M

⇒ with V1 = 5 mL = 5*10^-3 L

⇒ with M2 = TO BE DETERMINED

⇒ with V2 = 50 mL = 50 *10^-3 L

M2 = (M1*V1)/V2

M2 = (1.250 *10^-2 * 5*10^-3 L) / 50 *10^-3

M2 = 0.00125 M = 1.25 *10^-3 M

<u>Step 3:</u> Calculate dilution 1

M2 = (M1*V1)/V2

M2 = (1.25*10^-3 * 10 *10^-3)/(25*10^-3L)

M2 = 0.0005 M = 5*10^-4 M

<u>Step 4</u>: Calculate dilution 2

M2 = (M1*V1)/V2

M2 = (1.25*10^-3 * 10 * 7.5*10^-3)/(25*10^-3)

M2 = 0.000375 M = 3.75 * 10^-4 M

<u>Step 5:</u> Calculate dilution 3

M2 = (M1*V1)/V2

M2 = (1.25*10^-3 * 5*10^-3) /(25*10^-3)

M2 = 0.00025 M = 2.5 *10^-4 M

<u>Step 6</u>: Calculate dilution 4

M2 = (M1*V1)/V2

M2 = (1.25*10^-3 * 2.5*10^-3)/(25*10^-3)

M2 = 0.000125 M = 1.25 *10^-4 M

5 0
3 years ago
Helppppppppppppppppppppppppppp
Charra [1.4K]

Kinetic energy remains conserved in an elastic collision.

5 0
2 years ago
What three (3) factors determine the reactivity of elements? Explain and give examples of each.
Degger [83]

Explanation:

The three factors which determine the reactivity of elements are as follows.

(1) Number of valence electrons.

(2) Size of an atom.

(3) Electro negativity of an atom.

All these factors are explained as follows.

(1) Number of valence electrons

According to the octet rule, every atom requires to attain stability. Therefore, number of electrons in the outermost shell will decide the reactivity of an atom as every atom needs to fill its shells or sub shells as per the octet rule. As a result, the reactivity increases.

For example, the atomic number of chlorine is 17 and its electronic configuration is 1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}

In the 3p sub shell, there is deficiency of one electron. So, in order to attain stability chlorine atom will react readily with another species or atom which can either donate or share one electron.

Whereas an atom with completely fill shell will have low reactivity.

(2) Size of an atom

On moving down the group size of atom increases. As a result, the attraction between the nucleus and electrons decreases due to the shielding effect. Thus, the larger is an atom, the more easily it can give electrons. Therefore, the reactivity increases.

For example, the atomic number of calcium is 20 and its electronic configuration is 1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}

Also it is known that first shell of every atom can have 2 electrons, second shell can have 8 electrons, third shell can have 18 electrons and so on.

Since, calcium is larger in size as compared to beryllium and magnesium so it will readily loose 2 electrons to attain stability. Thus, it will attain a Ca^{2+} charge.

(3) Electro negativity of an atom

An atom with uneven distribution of electrons will acquire a certain amount of charge. Thus, it becomes polar in nature and in order to gain stability, the atom will either loose or gain electrons according to its charge.

For example, atomic number of fluorine is 9 and its electronic configuration is 1s^{2}2s^{2}2p^{5}.

So, in order to gain stability fluorine will readily accept 1 electron to completely fill its 2p sub shell. As a result, the electronic configuration will become 1s^{2}2s^{2}2p^{6}

Therefore, fluorine will have a charge of -1 because it has gained one electron.


 

3 0
3 years ago
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