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Ulleksa [173]
3 years ago
8

What is the mass number of 207Pb ? A: 289 B: 207 C: 125 D: 82

Chemistry
1 answer:
Sergio [31]3 years ago
3 0
207 is the mass number. 82 would be the atomic number
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Why are only certain colors absorbed by and emitted from an atom?
zavuch27 [327]
The way I would explain it is quite difficult to understand, so this is what Google says. "The wavelength (or equivalently, frequency) of the photon is determined by the difference in energy between the two states. These emitted photons form the element's spectrum. The fact that only certain colors appear in an element's atomic emission spectrum means that only certain frequencies of light are emitted." I hope this helped.
6 0
4 years ago
In the unbalanced equation given below, what is the element that is gaining electrons?
viktelen [127]

Hey there!:

HCl + MnO2 → MnCl2 + H2O + Cl2

* in HCl the oxidation state of Cl is -1 .

* on the product side the oxidation state is 0 .

* therefore Cl gains electrons .

* in  MnO2 the oxidation state of Mn is +4

* in MnCl2 the oxidation state of Mn is +2

Therefore Mn loses electrons

Answer A

Hope That helps!

4 0
3 years ago
Read 2 more answers
A 15.0 g piece of graphite is heated to 100.0°C and placed in a calorimeter. The
LenKa [72]

Answer:

0.714Jg^-10C^-1.

Explanation:

4 0
3 years ago
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The density of silver is 10.5 g/cm3. what would be the mass (in grams) of a piece of silver that occupies a volume of 23.6 cm3?
Keith_Richards [23]
Hey there : !

density = 10.5 g/cm³

volume = 23.6 cm³

therefore:

D = m / V

10.5 = m / 23.6

m = 10.5 * 23.6

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hope this helps!
6 0
3 years ago
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A galvanic cell at a temperature of is powered by the following redox reaction: 2Cr3 + 3Ca Suppose the cell is prepared with in
stira [4]

Answer:

2.13 V

Explanation:

The balanced equation of the reaction his;

2Cr^3+(aq) + 3Ca(s) -----> 2Cr(s) + 3Ca^2+(aq)

Since this is a galvanic cell then E°cell must be positive. It implies that calcium will be the anode and chromium will be the cathode since calcium is ahead of chromium in the electrochemical series.

E°anode= -2.87 V

E°cathode= -0.74 V

E°cell= E°cathode -E°anode

E°cell= -0.74 -(-2.87)

E°cell = 2.13 V

8 0
3 years ago
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