If 200 mL of water is evaporated from 400 mL of 0.5 M aqueous salt solution, what is the resulting concentration? 1. 2.5 × 10−1 M 2. 2.5 × 101 M 3. 2.5 × 100 M 4. 2.5 × 10−2 M 5. None of these

Answer:

- 0.028 °C

Explanation:

Where, ΔTf is the depression in water freezing point (ΔTf = ???°C).

Kf is the molal freezing point depression constant of the solvent (Kf = 1.86 °C/m).

m is the molality of AlCl₃ (m = 0.015 m).

∴ ΔTf = Kf.m = (1.86 °C/m)(0.015 m) = 0.0279 °C ≅ 0.028 °C.

∵ ΔTf = freezing point of pure water - freezing point of the solution in presence of AlCl₃.

∴  freezing point of the solution in presence of AlCl₃ = freezing point of pure water - ΔTf = 0.0 °C - 0.028 °C = - 0.028 °C.

just be postice and you will find the answer

Answer:

[tex]\boxed{\text{(D) 2 HCHO}_{2}}[/tex]

Explanation:

HCOOH + H₂O ⇌ H₃O⁺ + HCOO⁻

HCHO₂ is a weak acid. It dissociates only to a few percent, so there will be more HCHO₂ than H₃O⁺ present.

After H₂O, the most abundant species will be undissociated HCHO₂, so the answer will be either (B) or (D).

We can use an ICE table to organize the calculation of the pH.

                  HCOOH +H₂O ⇌ H₃O⁺ + HCOO⁻

I/mol·L⁻¹:        0.5                       0            0

C/mol·L⁻¹:       -x                        +x           +x

E/mol·L⁻¹:     0.5 - x                    x             x

[tex]K_{\text{a}} = \dfrac{\text{[H}_{3}\text{O}^{+}]\text{HCOO}^{-}]} {\text{[HCOOH]}} = 2 \times 10^{-4}\\\\\dfrac{x^{2}}{0.5-x} = 2 \times 10^{-4}[/tex]

Check for negligibility of x

[tex]\dfrac{ 0.5 }{2 \times 10^{-4}} = 2500 > 400.[/tex]

∴ x ≪ 0.5

[tex]\dfrac{x^{2}}{0.5} = 2 \times 10^{-4}[/tex]

x² = 0.5 × 2 × 10⁴ = 1 × 10⁻⁴

x = √(1 × 10⁻⁴) = 1 × 10⁻²

[H₃O⁺] = x mol·L⁻¹ = 1 × 10⁻² mol·L⁻¹

pH = -log[H₃O⁺] = -log(1 × 10⁻²) = 2

The correct answer is [tex]\boxed{\textbf{(D) 2 HCHO}_{2}}[/tex].

Answer:

The nervous system

Explanation:

The nervous system send messages from the brain to the muscles to move.

The nervous system, particularly the somatic nervous system, provides the impulses that enable the muscular system to function, allowing for a wide range of both voluntary and involuntary movements.

The muscles of the body, part of the muscular system, would not function without the nervous system providing the impulses that cause the muscles to act. This is particularly true for the skeletal muscles, which completely depend on signaling from the nervous system to work properly.

Our nervous system is divided into the somatic nervous system (SNS) and the autonomic nervous system, with the SNS responsible for the contraction of our skeletal muscles. This mechanism enables a wide range of voluntary and involuntary movements, like standing, walking, running, grasping items, and reflex actions; some of which happen automatically due to habit learning or procedural memory.

Responses can be voluntary, such as the contraction of skeletal muscles, or involuntary like the contraction of smooth muscles, regulation of cardiac muscles, and activation of glands.

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