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3 years ago

Use the data in the table above to calculate an approximate ΔH∘ in kilojoules for the synthesis of hydrazine from ammonia:

Chemistry

1 answer:

ankoles [38]3 years ago

8 0

DeltaH formation = deltaH of broken bonds - deltaH of formed bonds

Broken bonds: tiple bond N-N and H-H bond
Formed bonds: N-H and N-N bonds

You also have to take note of the molar coefficients

deltaH formation = [(N≡N) + 2 * (H-H)] - [4 * (N-H) + (N-N)]
= (945 + 2*436) - (4*390 + 240)
= 17 kJ/mol

The answer is 17 kJ/mol.

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Matter can exist as a solid, a liquid, or a gas. The solid state is distinguished by its ability to

Elina [12.6K]

Answer:

Explanation:

A solid is characterized by structural rigidity and resistance to a force applied to the surface. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire available volume like a gas. Solids molecules stay close to eachother maintaining its shape meaning it is in a ordered pattern.

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3 years ago

Enzymes work by _____. enzymes work by _____. decreasing the potential energy difference between reactant and product adding ene

Anton [14]

The appropriate answer is they decrease the potential energy difference between reactant and product. They do this by bringing products and reactants together at the active site on the enzyme molecule. Enzymes are biological catalysts. They increase the rate of a chemical reaction without being used up in the reaction itself. So one molecule of an enzyme is used many times to catalyze the reaction of other molecules.

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3 years ago

A student titrates a 20.00 mL sample of an aqueous borax solution with 1.03 M H2SO4. If 2.07 mL of acid are needed to reach the

RSB [31]

Answer:

The concentration of the borax solution is 0.1066 M

Explanation:

Step 1: Dtaa given

Volume of a sample of aqueous borax solution = 20.00 mL = 0.020 L

Molarity of H2SO4 = 1.03 M

Volume of the H2SO4 = 2.07 mL = 0.00207 L

Step 2: The balanced equation

Na2B4O7*10H2O(borax) + H2SO4 ⇆ Na2SO4 + 4 H3BO3 + 5 H2O

Step 3: Calculate molarity of borax solution

b*Ca*Va = a * Cb*Vb

⇒with B = the coefficient of H2SO4 = 1

⇒with Ca = the concentration of borax = TO BE DETERMINED

⇒with Va = the volume of borax = 0.020 L

⇒with a = the coefficient of borax = 1

⇒with Cb = the concentration of H2SO4 = 1.03 M

⇒with Vb = the volume of H2SO4 = 0.00207 L

Ca*0.020 L = 1.03 M * 0.00207 L

Ca = (1.03 * 0.00207) / 0.020

Ca = 0.1066 M

The concentration of the borax solution is 0.1066 M

6 0

3 years ago

Which of the following measurements (of different masses) is the most precise? A 6.2000g B 6.000000g C 6.24400g D 6.24444g

babymother [125]

Answer:

Explanation:

7 0

3 years ago

Lead ions can be precipitated from solution with KCl according to the following reaction:

MrRa [10]

Answer:

34.48 grams = Theoretical yield

The % yield is 85.85 %

Explanation:

Step 1: The balanced equation

Pb2+(aq) + 2KCl(aq) → PbCl2(s) + 2K+(aq)

For 1 mole Pb2+ consumed, we need 2 moles of KCl to produce 1 mole of PbCl2 and 2 moles of K+

Step 2: Given data

Mass of KCl = 28.8 grams

Mass of Pb2 = 25.6 grams

Mass of dried PbCl2 = 29.6 grams

Molar mass of Pb2+ = 207.2 g/mol

Molar mass of KCl = 74.55 g/mol

Molar mass of PbCl2 = 278.1 g/mol

Step 3: Calculate moles of Pb2+

Moles = mass / Molar mass

Moles Pb2+ = 25.6 grams / 207.2 g/mol = 0.124 moles

Step 4: Calculate moles of KCl

Moles = 28.8 grams / 74.55 g/mol = 0.386 moles

Step 5: Calculate limiting reactant

For 1 mole Pb2+ consumed, we need 2 moles of KCl

Pb2+ is the limiting reactant. It will completely ( 0.124 moles) be consumed. There will remain 0 moles

There will react 2* 0.124 = 0.248 moles of KCl. There will remain 0.386 - 0.248 = 0.138 moles of KCl

Step 6: Calculate number of moles of PbCl2

For 1 mole Pb2+ consumed, we need 2 moles of KCl to produce 1 mole of PbCl2 and 2 moles of K+

For 0.124 moles of Pb2+ consumed ,there will be produced 0.124 moles of PbCl2

Step 7: Calculate mass of PbCl2

Mass = Numbers of moles * Molar mass

mass PbCl2 =0.124 moles * 278.1 g/mol = 34.48 grams = Theoretical yield

Step 8: Calculate % yield

% yield = (actual yield / theoretical yield) * 100 = (29.6 grams / 34.48 grams) *100 % = 85.85 %

The % yield is 85.85 %

8 0

3 years ago