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2 years ago

Please...................

Chemistry

1 answer:

Elena L [17]2 years ago

8 0

I’m not sure but I hope someone tell you

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_____________________ held that all matter is made up of four “elements”— earth, air, fire, and water.

Novosadov [1.4K]

Answer:

Democritus

Explanation:

He spoke about matter was made of tiny particles which moved in empty space

4 0

3 years ago

Please help: A 0.200 M NaOH solution was used to titrate a 18.25 mL HF

algol [13]

The molar concentration of the original HF solution : 0.342 M

Further explanation

Given

31.2 ml of 0.200 M NaOH

18.2 ml of HF

Required

The molar concentration of HF

Solution

Titration formula

M₁V₁n₁=M₂V₂n₂

n=acid/base valence (amount of H⁺/OH⁻, for NaOH and HF n =1)

Titrant = NaOH(1)

Titrate = HF(2)

Input the value :

$\tt 0.2\times 31.2\times 1=M_2\times 18.25\times 1\\\\M_2=0.342$

7 0

3 years ago

An aqueous solution contains 0.29 M of benzoic acid (HA) and 0.16 M of sodium benzoate (A-). If the pH of this solution was meas

Inga [223]

Answer:

pKa = 4.89.

Explanation:

We can solve this problem by using the Henderson-Hasselbach equation, which states:

pH = pKa + log $\frac{[A^-]}{[HA]}$

In this case [A⁻] is the concentration of sodium benzoate and [HA] is the concentration of benzoic acid.

We input the given data:

4.63 = pKa + log $\frac{0.16}{0.29}$

And solve for pKa:

pKa = 4.89

3 0

3 years ago

Given the following information:Br2 bond energy = 193 kJ/mol F2 bond energy = 154 kJ/mol 1/2Br2(g) + 3/2F2(g) -> BrF3(g) = –3

arlik [135]

Answer:

C) 712 KJ/mol

Explanation:

ΔH°r = Σ Eb broken - Σ Eb formed

1/2Br2(g) + 3/2F2(g) → BrF3(g)

∴ ΔH°r = - 384 KJ/mol

∴ Br2 Eb = 193 KJ/mol

∴ F2 Eb = 154 KJ/mol

⇒ Σ Eb broken = (1/2)(Br-Br) + (3/2)(F-F)

⇒ Σ Eb broken = (1/2)(193 KJ/mol) + (3/2)(154 KJ/mol) = 327.5 KJ/mol

∴ Eb formed: Br-F

⇒ Σ Eb formed (Br-F) = Σ Eb broken - ΔH°r

⇒ Eb (Br-F) = 327.5 KJ/mol - ( - 384 KJ/mol )

⇒ Eb Br-F = 327.5 KJ/mol + 384 KJ/mol = 711.5 KJ/mol ≅ 712 KJ/mol

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3 years ago

Match the academic requirements with the careers . Cosmetologist

inessss [21]

Answer:

Technical program - cosmetologist

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3 years ago