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SIZIF [17.4K]
3 years ago
12

An atom has a mass number of 31 and an atomic number of 15. How many protons and how many neutrons are in this atom? Show the nu

clear symbol for this atom.

Chemistry
1 answer:
vaieri [72.5K]3 years ago
5 0
The atomic number of an atom is equal to the amount of protons the atom has, and the mass number is equal to the sum of the protons and neutrons. Therefore:

let protons = p
let neutrons = n                                                  
let atomic mass = a

P+N=A 
15+n=31
n=16

There are 16 neutrons in this atom.
(See attached for nuclear symbol)

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g Calculate the time (in min.) required to collect 0.0760 L of oxygen gas at 298 K and 1.00 atm if 2.60 A of current flows throu
lozanna [386]

Answer:

7.67 mins.

Explanation:

Data obtained from the question include the following:

Volume (V) = 0.0760 L

Temperature (T) = 298 K

Pressure (P) = 1 atm

Current (I) = 2.60 A

Time (t) =?

Next, we shall determine the number of mole (n) of O2 contained in 0.0760 L.

This can be obtained by using the ideal gas equation as follow:

Note:

Gas constant (R) = 0.0821 atm.L/Kmol

PV = nRT

1 x 0.0760 = n x 0.0821 x 298

Divide both side by 0.0821 x 298

n = 0.0760 / (0.0821 x 298)

n = 0.0031 mole

Next, we shall determine the quantity of electricity needed to liberate 0.0031 mole of O2.

This is illustrated below:

2O²¯ + 4e —> O2

Recall:

1 faraday = 1e = 96500 C

4e = 4 x 96500 C

4e = 386000 C

From the balanced equation above,

386000 C of electricity liberated 1 mole of O2.

Therefore, X C of electricity will liberate 0.0031 mole of O2 i.e

X C = 386000 X 0.0031

X C = 1196.6 C

Therefore, 1196.6 C of electricity is needed to liberate 0.0031 mole of O2

Next, we shall determine the time taken for the process. This can be obtained as follow:

Current (I) = 2.60 A

Quantity of electricity (Q) = 1196.6 C

Time (t) =?

Q = It

1196.6 = 2.6 x t

Divide both side by 2.6

t = 1196.6/2.6

t = 460.23 secs.

Finally, we shall convert 460.23 secs to minute. This can be achieved by doing the following:

60 secs = 1 min

Therefore,

460.23 secs = 460.23/60 = 7.67 mins

Therefore, the process took 7.67 mins.

7 0
4 years ago
If a car travels 60 miles in 3 hours, what is the car’s speed?
marysya [2.9K]
Answer = 20 mph !
Hope this helps
6 0
4 years ago
Read 2 more answers
35.0 grams of nitrogen gas reacts with 60.0 grams of hydrogen gas: N2 + 3H2--> 2NH3
Misha Larkins [42]

Explanation:

Moles of N2 = 35.0g / (28g/mol) = 1.25mol

Moles of H2 = 60.0g / (2g/mol) = 30.0mol

Since 1.25mol * 3 < 30.0mol, nitrogen is limiting.

Moles of NH3 = 1.25mol * 2 = 2.50mol.

Mass of NH3 = 2.50mol * (17g/mol) = 42.5g.

30.0mol - 1.25mol * 3 = 26.25mol.

Excess mass of H2

= 26.25mol * (2g/mol) = 52.5g.

6 0
3 years ago
Wheen 56j of heat are added to 11g of liquid, its temperature rises from 10.4 degrees celsius to 12 degrees celsius. What is the
svetoff [14.1K]

c = 3.2 \; \text{J} \cdot \text{kg}^{-1} \cdot \text{K}^{-1}

  • Energy change Q = 56 \; \text{J}
  • Mass being heated m = 11 \; \text{g}
  • Temperature change \Delta T = 12 - 10.4 = 1.6\;^{\text{o}}\text{C} which is the same as 1.6 \;\text{K}.

Heat capacity measures the energy required to raise the temperature of a unit mass of a substance by a unit degree. Therefore

c = Q / (m \cdot \Delta T) = 56/(11 \times (12 - 10.4)) = 3.2 \; \text{J} \cdot \text{kg}^{-1} \cdot \text{K}^{-1}


7 0
4 years ago
Read 2 more answers
a) Calculate the mass of Li formed by electrolysis of molten LiCl by a current of 8.2 104 A flowing for a period of 14 hr. Assum
Sonja [21]

a) Answer:

= 210,000 gram or 210 Kg  

Explanation:

14 hr is equivalent to;

= 14 × 3600 s

But; 

8.2x10^4 A = 8.2x10^4 Coulomb /second = 8.2x10^4 C/s  

1 Faraday = 96485C  

Molar mass of Li: 6.941 g/mol  

Therefore;

{(8.2x10^4 C/s)×(14×3600s)×(6.941 g/mol)/(96485C/mol)}×70%  

= 2.1x10^5 gram  or 210 kg

b.  Answer;

= 0.23 kWh/mol

Explanation and solution;

Energy per mole is given by;

(96485C/mol) × (8.4V) = 8.10x10^5 (J/mol)  

= 8.10x10^5 (Ws/mol)  

Divide by 3600s/h to get:  

= 8.10x10^5 (Ws/mol)

= 225 Wh/mol

= 0.23 kWh/mol

8 0
4 years ago
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