Petroleum and coal can be mined from the continental shelf. t/f

Answer : The correct option is, the sum of the enthalpy changes of the intermediate reactions.

Explanation :

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

For example :

The formation reaction of CO will be,

The intermediate balanced chemical reaction will be,

(1)    

(2)    

The expression for enthalpy of formation of CO is,

where,

n = number of moles

By adding reaction 1 and reverse reaction of reaction 2, we get the enthalpy of formation of CO.

Hence, the correct option is, the sum of the enthalpy changes of the intermediate reactions.

Metals experience plastic deformation when a specific amount of pressure and temperature is applied to them. Most metals have low specific heat. Because of their low specific heat, they easily get hot when heat is applied to them.

Answer: The description it provides reactants with sufficient energy for bonds to break and reform best explains the role of activation energy in a chemical reaction.

Explanation:

Activation energy is defined as the minimum amount of required energy so that a chemical reaction can initiate.

As a result, it provides the reactants with certain amount of energy so that they will get the necessary amount of energy to break their bond and then  form new bonds.

Thus, we can conclude that the description it provides reactants with sufficient energy for bonds to break and reform best explains the role of activation energy in a chemical reaction.

Answer:

• The third chice: 0.0750 M Na₂SO₄

Explanation:

Assume 100% ionization:

1) 0.100 M solution K₂SO₄

• K₂SO4 (aq) → 2K⁺ (aq) + SO₄²⁻ (aq)

• Mole ratios: 1 mol K₂SO4 : 2 mol K⁺  + 1 mol SO₄²⁻ (aq) : 3 mol ions. This is 1 : 3

• At constant volume, the mole ratios are equal to the concentration ratios (M).

• 1  M K₂SO₄: 3 M ions = 0.100 M K₂SO₄ / x ⇒ x = 0.300 M ions

This means, that you have to find which of the choices is a solution that contains the same 0.300 M ion concentration.

2) 0.0800 M Na₂CO₃

• Na₂CO₃ (aq) → 2 Na⁺ + CO₃⁻

• 1 M Na₂CO₃ / 3 M ions = 0.0800M / x ⇒ x = 0.0267 M ions

This is not equal to 0.300 M, so this solution would not contain the same total concentration as a 0.100 M solution of K₂SO₄, and is not the right answer.

3)  0.100 M NaCl

• NaCl → Na⁺ + Cl⁻

• 1 M NaCl / 2 M ions = 0.100 M NaCl / x ⇒ x = 0.200 M ions

This is not equal to 0.300 M ion, so not a correct option.

4) 0.0750 M Na₃PO₄

• Na₃PO₄ → 3Na⁺ + PO₄³⁻

• 1 M Na₃PO₄ / 4 M ions = 0.0750 M Na₃PO₄ / x ⇒ x = 0.300 M ions

Hence, this ion concentration is equal to the ion concentration of a 0.100 M solution of K₂SO₄, and is the correct choice.

5)  0.0500 M NaOH

• NaOH → Na⁺ + OH⁻

• 1 M NaOH / 2 mol ions = 0.0500 M NaOH / x ⇒ x = 0.100 M ions

Not equal to 0.300 M, so wrong choice.

Answer : Option A) Dry media

Explanation : i) Dry media is a media that deposits graphite, charcoal, pastels, ordinary pencils, then moistened with a wet brush to get various painterly effects on the paper fibers.

ii) Silverpoint - Silverpoint media uses red chalk or traces of black pencil on white-coated paper usually the manuscripts,

iii) Ink Painting - Uses various inks on the paper.

iv) Liquid media - uses liquid pigments suspended in some base which in liquid state that soaks the paper.