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3 years ago

Why is the mass in amu of a carbon-12 atom reported as 12.011 in the periodic table of the elements?

1 answer:

7 0

The mass of an element listed in the Periodic Table is the weighted average of all its naturally occurring isotopes.

Naturally occurring carbon is about

99 % carbon-12 (12.000 u) + 1 % carbon-13 (13.003 u).

That extra carbon-13 makes the <em>average atomic mass</em> greater than 12.000 u.

You might be interested in

What is the pressure of 5.0 mol nitrogen (N2) gas in a 2.0 L container at 268

CaHeK987 [17]

Answer: 54.94atm

Explanation: Please see attachment for explanation

8 0

3 years ago

What is the empirical formula for a substance that is composed of 40.66% carbon, 8.53% Hydrogen,23.72% Nitrogen, and 27.09% Oxyg

prohojiy [21]

Answer:

THE EMPIRICAL FORMULA OF THE SUBSTANCE IS C2H5NO

Explanation:

The steps involved in calculating the empirical formula of this substance in shown in the table below:

Element Carbon Hydrogen Nitrogen Oxygen

1. % Composition 40.66 8.53 23.72 27.09

2. Mole ratio =

%mass/ atomic mass 40.66/12 8.53/1 23.72/14 27.09/16

= 3.3883 8.53 1,6943 1.6931

3. Divide by smallest

value (0.6931) 3.3883/1.6931 8.53/1.6931 1.6943/1.6931 1.6931/1.6931

= 2.001 5.038 1.0007 1

4. Whole number ratio 2 5 1 1

The empirical formula = C2H5NO

7 0

3 years ago

The half-life of nitrogen-13 is 10.0 minutes. if you begin with 53.3 mg of this isotope, what mass remains after 25.9 minutes ha

zimovet [89]

Hello!

The half-life is the time of half-disintegration, it is the time in which half of the atoms of an isotope disintegrate.

We have the following data:

mo (initial mass) = 53.3 mg

m (final mass after time T) = ? (in mg)

x (number of periods elapsed) = ?

P (Half-life) = 10.0 minutes

T (Elapsed time for sample reduction) = 25.9 minutes

Let's find the number of periods elapsed (x), let us see:

$T = x*P$

$25.9 = x*10.0$

$25.9 = 10.0\:x$

$10.0\:x = 25.9$

$x = \dfrac{25.9}{10.0}$

$\boxed{x = 2.59}$

Now, let's find the final mass (m) of this isotope after the elapsed time, let's see:

$m = \dfrac{m_o}{2^x}$

$m = \dfrac{53.3}{2^{2.59}}$

$m \approx \dfrac{53.3}{6.021}$

$\boxed{\boxed{m \approx 8.85\:mg}}\end{array}}\qquad\checkmark$

I Hope this helps, greetings ... DexteR! =)

3 0

3 years ago

Calculate the molecular weight of a substance. In which the solution of this substance in the water has a concentration of 7 per

Eduardwww [97]

Answer : The molecular weight of a substance is 157.3 g/mol

Explanation :

As we are given that 7 % by weight that means 7 grams of solute present in 100 grams of solution.

Mass of solute = 7 g

Mass of solution = 100 g

Mass of solvent = 100 - 7 = 93 g

Formula used :

$\Delta T_f=i\times K_f\times m\\\\T_f^o-T_f=k_f\times\frac{\text{Mass of substance(solute)}\times 1000}{\text{Molar mass of substance(solute)}\times \text{Mass of water(solvent)}}$

where,

$\Delta T_f$ = change in freezing point

$T_f^o$ = temperature of pure water = $0^oC$

$T_f$ = temperature of solution = $-0.89^oC$

$K_f$ = freezing point constant of water = $1.86^oC/m$

m = molality

Now put all the given values in this formula, we get

$(0-(-0.89))^oC=1.86^oC/m\times \frac{7g\times 1000}{\text{Molar mass of substance(solute)}\times 93g}$

$\text{Molar mass of substance(solute)}=157.3g/mol$

Therefore, the molecular weight of a substance is 157.3 g/mol

7 0

3 years ago

How many hydrogen atoms are found in the<br> hydrate (NH4)3PO4.5H2O?

igomit [66]

Answer:

Explanation:

3x4+ 5x2

3 0

2 years ago