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Anit [1.1K]
3 years ago
9

How is the atomic mass of an element calculated? A. by determining the number of electrons in the outer orbital B.by determining

the number of protons in the nucleus C. by taking the weighted averages of naturally occurring isotopes of that element D. by dividing its mass by that of the carbon-12 atom
Chemistry
2 answers:
Vaselesa [24]3 years ago
7 0

By adding together the number of protons and neutrons and multiplying by 1 amu, you can calculate the mass of the atom.

aalyn [17]3 years ago
6 0

I believe that it is B

You might be interested in
The heat of fusion for a substance is 122 joules per gram. How many joules of heat are need to melt 7.50 grams of this substance
daser333 [38]
<h3>Answer:</h3>

915 Joules

<h3>Explanation:</h3>
  • The heat of fusion is the heat that is required to convert a given mass of a substance from solid state to liquid state without change in temperature.
  • In this case, we are given specific heat of a substance as 122 joules per gram
  • It means that amount of heat equivalent to 122 joules is required to change 1 gram of the substance from solid state to liquid state.
  • Therefore, we can determine the amount of heat needed to change 7.5 grams of the substance from solid to liquid state.

1 g = 122 Joules

7.5 g = ?

       = 122 × 7.5

      = 915 Joules

Thus, 7.5 g of the substance at its melting point will require 915 Joules of heat to melt.

4 0
3 years ago
Given these reactions, where X represents a generic metal or metalloid 1) H2(g)+12O2(g)⟶H2O(g)ΔH1=−241.8 kJ 1) H2(g)+12O2(g)⟶H2O
Bond [772]

Answer:

ΔH = -793,6 kJ

Explanation:

It is possible to obtain ΔH of this reaction using Hess's law that says you can sum the half-reactions ΔH to obtain the ΔH of the global reaction:

If half-reactions are:

1) H₂(g) + ¹/₂O₂(g) ⟶ H₂O(g) ΔH₁ = −241.8 kJ

2) X(s) + 2Cl₂(g) ⟶ XCl₄(s) ΔH₂ = +356.9 kJ  

3) ¹/₂H₂(g) + ¹/₂Cl₂(g) ⟶ HCl(g) ΔH₃ = −92.3 kJ

4) X(s) + O₂(g) ⟶ XO₂(s) ΔH₄ = −639.1 kJ

5) H₂O(g) ⟶ H₂O(l) ΔH₅ = −44.0 kJ

The sum of (4) + 4×(3) - (2) - 2×(1) - 2×(5) is:

(4) X(s) + O₂(g) ⟶ XO₂(s) ΔH = −639.1 kJ

+4×(3) 2H₂(g) + 2Cl₂(g) ⟶ 4HCl(g) ΔH = −369,2 kJ

-(2) XCl₄(s) ⟶ X(s) + 2Cl₂(g) ΔH = -356,9 kJ

-2×(1) 2H₂O(g) ⟶ 2H₂(g) + O₂(g) ΔH = +483,6 kJ

-2×(5) 2H₂O(l) ⟶ 2H₂O(g) ΔH = +88.0 kJ

= <em>XCl₄(s) + 2H₂O(l) ⟶ XO₂(s) + 4HCl(g)</em>

Where ΔH is:

ΔH = -639,1 kJ -369,2 kJ -356,9 kJ +483,6 kJ +88,0 kJ

<em>ΔH = -793,6 kJ</em>

I hope it helps!

5 0
3 years ago
A gas at 928 kpa, 129 C occupies a volume of 569 L. Calculate the volume at 319 kpa and<br> 32 C.
lisabon 2012 [21]

Answer:

1255.4L

Explanation:

Given parameters:

P₁  = 928kpa

T₁  = 129°C

V₁  = 569L

P₂ = 319kpa

T₂  = 32°C

Unknown:

V₂  = ?

Solution:

The combined gas law application to this problem can help us solve it. It is mathematically expressed as;

           \frac{P_{1} V_{1} }{T_{1} }   = \frac{P_{2} V_{2} }{T_{2} }

P, V and T are pressure, volume and temperature

where 1 and 2 are initial and final states.

Now,

 take the units to the appropriate ones;

             kpa to atm,  °C to K

P₂ = 319kpa in atm gives 3.15atm

P₁  = 928kpa gives 9.16atm

T₂  = 32°C gives 273 + 32  = 305K

T₁  = 129°C gives 129 + 273  = 402K

Input the values in the equation and solve for V₂;

        \frac{9.16  x 569}{402}   = \frac{3.15 x V_{2} }{305}

       V₂   = 1255.4L

4 0
3 years ago
How many grams of neutral salt will be obtained in the reaction of calcium oxide with 200 cm 3 of phosphoric acid solution whose
katen-ka-za [31]

Answer:

9.3 g of Ca3(PO4)2

Explanation:

We'll begin by writing the balanced equation for the reaction. This is illustrated below:

3CaO + 2H3PO4 —> Ca3(PO4)2 + 3H2O

Next, we shall determine the number of mole of H3PO4 present in 200 cm³ of 0.3 mol/dm³ phosphoric acid (H3PO4) solution. This can be obtained as follow:

Molarity of H3PO4 = 0.3 mol/dm³

Volume = 200 cm³ = 200 cm³/1000 = 0.2 dm³

Mole of H3PO4 =?

Molarity = mole /Volume

0.3 = mole of H3PO4 /0.2

Cross multiply

Mole of H3PO4 = 0.3 × 0.2

Mole of H3PO4 = 0.06 mole

Next, we shall determine the number of mole of the salt, Ca3(PO4)2, obtained from the reaction. This can be obtained as shown below:

3CaO + 2H3PO4 —> Ca3(PO4)2 + 3H2O

From the balanced equation above,

2 moles of H3PO4 reacted to produced 1 mole of Ca3(PO4)2.

Therefore, 0.06 moles of H3PO4 will react to produce = (0.06 × 1)/2 = 0.03 mole of Ca3(PO4)2.

Thus, 0.03 mole of Ca3(PO4)2 is produced from the reaction.

Finally, we shall determine the mass of Ca3(PO4)2 produced as follow:

Mole of Ca3(PO4)2 = 0.03 mole

Molar mass of Ca3(PO4)2 = (40×3) + 2[31 + (16×4)]

= 120 + 2[31 + 64]

= 120 + 2[95]

= 120 + 190

= 310 g/mol

Mass of Ca3(PO4)2 =?

Mole = mass /Molar mass

0.03 = mass of Ca3(PO4)2 / 310

Cross multiply

Mass of Ca3(PO4)2 = 0.03 × 310

Mass of Ca3(PO4)2 = 9.3 g

Thus, 9.3 g of Ca3(PO4)2 was obtained from the reaction.

6 0
2 years ago
Even though the neighborhood shown by the green star was not next to any of these fires, how was the neighborhood affected by th
iogann1982 [59]
Im pretty sure the answers b

7 0
3 years ago
Read 2 more answers
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