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3 years ago

What is a sign that a chemical change has occurred?

Chemistry

2 answers:

blondinia [14]3 years ago

3 0

Answer:

The production of heat, light, or smoke is observed.

vladimir1956 [14]3 years ago

3 0

The production of heat, light or smoke is observed and the state of matter has changed

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At what point is a base no longer added during a titration?

nordsb [41]

Answer:

when the pH increases suddenly in the flask

Explanation:

I think it's right. :)

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3 years ago

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Which metals or non-metals are liquid at a room temperature of 25°C?

irakobra [83]

Answer:

gallium

Explanation:

it is the old melting in a hot cup of coffee spoon

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3 years ago

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Write a balanced half-reaction describing the reduction of aqueous vanadium(V) cations to aqueous vanadium(I) cations.

11Alexandr11 [23.1K]

Explanation:

Reduction is a chemical reaction in which electrons are gained by one of the atoms taking part in the reaction and lowering of an oxidation state of that atom.

Reduction takes place at the cathode.

In aqueous, vanadium(V) is present in +5 oxidation state which on reduction changes to vanadium(I) with +1 oxidation state.

The half reaction is :

$V^{5+}(aq)+4e^- \rightarrow V^{1+}(aq)$

5 0

3 years ago

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calculate the wavelength of light associated with the transition from n=1 to n=3 in the hydrogen atom?

inessss [21]

Answer:

$\Delta E=E_{final}-E_{initial}$

$\Delta E=-1312[\frac{1}{(n_f^2)}-\frac {1}{(n_i^2 )}]KJ mol^{-1}$

$\Delta E=-1312[\frac{1}{3^2)}-\frac {1}{(1^2 )}]KJ mol^{-1}$

$\Delta E=-1312[\frac{1}{(9)}-\frac {1}{(1 )}]KJ mol^{-1}$

$\Delta E=-1312[0.111-1]KJ mol^{-1}$

$\Delta E=1166 KJ mol^{-1}$

$\frac{=1166,000 \mathrm{J}}{6.022 \times 10^{23} \text { photons }}$

$=193623 \times 10^{-23} \frac {J}{photon}$

$\Delta E=1.93623 \times 10^{-18} \frac {J}{photon}$

$\Delta E=\frac {h\times c}{\lambda} \\\\=\frac {(6.626\times 10^{-34} J s \times 3 \times 10^8 ms^{-1})}{\lambda}$

h is planck's constant

c is the speed of light

λ is the wavelength of light

$\lambda =\frac {h\times c}{\Delta E}\\\\=\frac {(6.626\times10^{-34} J s\times3 \times 10^8 ms^{-1})}{(1.93623\times10^{-18} J/photon)}$

Wavelength

$\lambda =10.3 \times 10^{-8} m \times \frac {(10^9 nm)}{1m} =103 nm (Answer)$

Thus, the wavelength of light associated with the transition from n=1 to n=3 in the hydrogen atom is 103 nm.

7 0

3 years ago

Changing the number of protons in an atom ONLY changes the weight of an atom. Need help ASAP

likoan [24]

Answer:

Explanation:

protons and electrons are equal to atomic number

3 0

3 years ago