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3 years ago

If an atom of sodium has 11 protons, what is its approximate atomic mass?

1 answer:

7 0

23. The atomic mass is calculated by adding the number of protons and neutrons. However, you cannot guess the number of neutrons. Refer to the periodic table. The atomic mass/mass no of Sodium is 23.

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For the reaction represented by the equation Fe + H2O ® Fe2O3 + H2, how many moles of iron(III) oxide are produced from 285 g of

schepotkina [342]

Balanced equation: 2Fe + 3H2O → Fe2O3 +3H2

Convert g to mols:

285/55.845 = 5.1034 mols

Mole ratio of Iron and Iron (III) Oxide: 2:1

5.1034/2 = 2.5517 mols

8 0

3 years ago

The NaCl crystal structure consists of alternating Na⁺ and Cl⁻ ions lying next to each other in three dimensions. If the Na⁺ rad

Yuliya22 [10]

Answer : The radii of the two ions Cl⁻ ion and Na⁺ ion is, 181 and 102 pm respectively.

Explanation :

As we are given that the Na⁺ radius is 56.4% of the Cl⁻ radius.

Let us assume that the radius of Cl⁻ be, (x) pm

So, the radius of Na⁺ = $x\times \frac{56.4}{100}=(0.564x)pm$

In the crystal structure of NaCl, 2 Cl⁻ ions present at the corner and 1 Na⁺ ion present at the edge of lattice.

Thus, the edge length is equal to the sum of 2 radius of Cl⁻ ion and 2 radius of Na⁺ ion.

Given:

Distance between Na⁺ nuclei = 566 pm

Thus, the relation will be:

$2\times \text{Radius of }Cl^-+2\times \text{Radius of }Na^+=\text{Distance between }Na^+\text{ nuclei}$

$2\times x+2\times 0.564x=566$

$2x+1.128x=566$

$3.128x=566$

$x=180.9\approx 181pm$

The radius of Cl⁻ ion = (x) pm = 181 pm

The radius of Na⁺ ion = (0.564x) pm = (0.564 × 181) pm =102.084 pm ≈ 102 pm

Thus, the radii of the two ions Cl⁻ ion and Na⁺ ion is, 181 and 102 pm respectively.

4 0

3 years ago

The half life of a certain radioactive element is 800 years. How old is an object if only 12.5% of radioactive atoms in it remai

Levart [38]

Given, half life of a certain radioactive element = 800 years.

Amount of substance remaining at time t = 12.5%

Lets consider the initial amount of the radioactive substance = 100%

Using the half life equation:

A = A₀(1/2)^t/t₁/₂

where A₀ is the amount of radioactive substance at time zero and A is the amount of radioactive substance at time t, and t₁/₂ is the half-life of the radioactive substance.

Plugging the given data into the half life equation we have,

12.5 = 100 . (1/2)^t/800

12.5/100 = (1/2)^t/800

0.125 = (0.5)^t/800

(0.5)^3 = (0.5)^t/800

3 = t/800

t = 2400 years

Thus the object is 2400 years old.

6 0

4 years ago

Koi Hain Jo bat kr le mujh se :/

Studentka2010 [4]