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3 years ago

Which is the best way to determine if an object is made of pure gold?

Chemistry

1 answer:

netineya [11]3 years ago

3 0

Answer:

Acid?

Explanation:

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A chemistry graduate student is given 500. mL of a 0.20 M chloroacetic acid (HCH2ClCO2) solution. Chloroacetic acid is a weak ac

zhenek [66]

Answer:

12 g of choloracetic acid

Explanation:

The buffer equilibrium is:

HCH₂ClCO₂ ⇄ CH₂ClCO₂⁻ + H⁺

pka= -log ka =

Ka: 1,3x10⁻³ = [CH₂ClCO₂⁻] [H⁺] / [HCH₂ClCO₂]

By Henderson-Hasselbalch equation:

pH = pka + log₁₀ [A⁻] / [HA]

3,01 = 2,89 + log₁₀ [A⁻] / [HA]

1,318 = [A⁻] / [HA]

As molar concentration of chloroacetic acid (HA) is 0,20M

[A⁻] = 0,26 mol/L

The volume is 500 mL ≡ 0,5 L

0,26mol/L × 0,5 L = 0,13 moles of chloroacetic acid. In grams:

0,13 mol × (94,5g / 1mol) = <em>12 g of choloracetic acid</em>

I hope it helps!

3 0

3 years ago

You observe 2 waves named alpha and beta. The alpha wave has a frequency of 5 Hz and the beta wave has a frequency of 2 Hz. Base

MAVERICK [17]

Answer:

shorter wavelength = alpha wave

Explanation:

Given that,

The alpha wave has a frequency of 5 Hz and the beta wave has a frequency of 2 Hz.

We need to compare the wavelengths of these two waves.

For alpha wave,

$\lambda_1=\dfrac{c}{f_1}\\\\\lambda_1=\dfrac{3\times 10^8}{5}\\\\=6\times 10^7\ m$

For beta wave,

$\lambda_2=\dfrac{c}{f_2}\\\\\lambda_2=\dfrac{3\times 10^8}{2}\\\\=15\times 10^7\ m$

From the above calculations, we find that the wavelength of the alpha wave is shorter than the wavelength of the beta wave.

8 0

2 years ago

How many valence electrons is each element trying to obtain?

lukranit [14]

An element is always trying to have 8 valence electrons. Each element must obtain a different number to come to a total of 8

3 0

3 years ago

The specific heat capacity of a pure substance can be found by dividing the heat needed to change the temperature of a sample of

kupik [55]

Answer:

See below

Explanation:

ΔQ = m c T ΔQ = heat required(J) m = mass (g) T = C° temp change

c = heat capacity in J/g-C

4 0

2 years ago

What is the frequency of radiation whose wavelength is 2.51 x 10 -7m?

hodyreva [135]

The frequency of radiation : 1.2 x 10¹⁵ Hz

<h3>Further explanation </h3>

Radiation energy is absorbed by photons

The energy in one photon can be formulated as

$\large{\boxed{\bold{E\:=\:h\:.\:f}}}$

Where

h = Planck's constant (6,626.10⁻³⁴ Js)

f = Frequency of electromagnetic waves

c = speed of light

= 3.10⁸ m/s

λ = wavelength

Wavelength-λ is 2.51 x 10⁻⁷m

The frequency :

$\tt f=\dfrac{3.10^8}{2.51\times 10^{-7}}=1.2\times 10^{15}$

8 0

2 years ago