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2 years ago

12

A radioactive nuclide is used to detect eye tumors. An atom of this radionuclide contains 15 protons, 15 electrons, and 17 neutr

ons. Which is symbol of this radionuclide?

2 answers:

Mazyrski [523]2 years ago

8 0

Answer: $_{15}^{32}\textrm {P}$

Explanation:- Atomic number is the number of protons or the number of electrons.

Mass number is the sum of number of protons and number of neutrons.

Atomic number = number of electrons= number of protons = 15

Mass number = number of protons + number of neutrons= 15+17= 32.

The representation of element is :

where Z= atomic number, A= mass number , X= chemical symbol of element

The representation of the element with atomic number 15 and mass number 32 is : $_{15}^{32}\textrm {P}$

choli [55]2 years ago

3 0

Knowing that the number of protons of an element is equivalent to its atomic number, it can be determined from the periodic table of elements that this radiosonde is phosphorus. Since the number of its neutrons is 17, it can also be determined that its atomic mass is n + p = 15 + 17 = 32. This means the isotope is phosphorus-32.<span />

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Nezavi [6.7K]

Answer:

1

The heat of reaction is $Q = 170.92 \ J$

The enthalpy is $\Delta H = -170.91 \ J$

2

The concentration of HCl is $M__{HCl}} =2.468 M$

Explanation:

From the question we are told that

The volume of $NaOH$ is $V_{NaOH} = 45 \ cm^3 = \frac{45} {1000} = 0.045 L$

The number of concentration of $NaOH$ is $M__{NaOH}} = 2M$

The volume of HCl is $V_{HCl} = 20 cm^3$

The number of concentration of $HCl$ is $M__{HCl}} = 1 M$

The temperature difference is $\Delta T = 9.4 ^o C$

Now the heat of reaction is mathematically represented as

$Q = m * c_p * \Delta T$

Where

$c_p$ is the specific heat of water with value $c_p = 4200 J /kg ^o C$

$m = m__{NaOH}} + m__{HCl}}$

Now $m__{NaOH}} = V_{NaOH} * M_{NaOH} * Z_{NaOH}$

where $Z_{NaOH}$ is the molar mass of NaOH with the value of 0.04 kg/mol

So $m__{NaOH}} = 0.045 * 2 * 0.040$

$m__{NaOH}} =0.0036\ kg$

While

$m__{HCl}} = V_{HCl} * M_{HCl} + Z_{HCl}$

Where $Z_{HCl}$ is the molar mass of $HCl$ with the value of 0.03646 kg/mol

$m__{NaOH}} = 0.020 * 1 * 0.03646$

$m__{NaOH}} = 0.000729 kg$

So

$m = 0.0036 + 0.000729$

$m = 0.00433$

=> $Q = 0.00433 * 4200 * 9.4$

$Q = 170.92 \ J$

The enthalpy is mathematically represented as

$\Delta H = - Q$

=> $\Delta H = -170.91 \ J$

From the second question we are told that

The volume of HCl is $V_{HCl_1} = 10cm^3 = \frac{10}{1000} = 0.010 L$

The volume of NaOH is $V_{NaOH_1 } = 30 cm^3 = \frac{30}{1000} = 0.03 L$

The concentration of NaOH is $M_{NaOH} = 2 M$

The first temperature change is $\Delta T = 4.5 ^oC$

The second volume of $V_{HCl_2} = 20 cm^3 = \frac{20}{1000 } = 0.020 m^3$

The mass of NaOH is

$m__{NaOH}} = V_{NaOH} * M_{NaOH} * Z_{NaOH}$

substituting values

$m__{NaOH}} = 0.03 * 2 * 40$

$m__{NaOH}} = 3.6 \ g$

The mass of the product formed is

$m = \frac{Q}{c_p * \Delta T}$

substituting values

$m = \frac{170.91}{4200 * 9} * 1000$

The multiplication by 1000 is to convert it from kg to grams

$m = 4.5 g$

Now the mass of HCl is

$m__{HCl}} = m - m__{NaOh}}$

substituting values

$m__{HCl}} = 4.5 -3.6$

$m__{HCl}} = 0.9 \ g$

Now the concentration of HCl is

$M__{HCl}} = \frac{m_{HCl}}{(Z_{HCl} * *1000) * V_{HCl_1}}}$

The multiplication of $Z_{HCl}$ is to convert it from kg/mol to g/mol

$M__{HCl}} = \frac{0.9}{36.46 * 0.01}}$

$M__{HCl}} =2.468 M$

3 0

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CH3CN major species present when dissolved in water

Margaret [11]

Answer: CH₃CN and H₂O.

Explanation:

1) The spieces present in a solution may be either the molecules, in case of covalent compounds, or ions, in case of ionic compounds that dissociate (ionize).

2) Both, CH₃CN and H₂O are covalent (polar covalent) substances, so they do not ionize and the spieces in the solution are the molecules per se.

3) In solution, the molecules of H₂O will solvate the molecules of CH₃CN, meaning that H₂O molecules are able to separate the molecules of CH₃N from each other, and so every molecule of CH₃CN will end surrounded by many molecules of H₂O.

This happens because the interaction between the polar molecules of the two different compounds is strong enough to overcome the intermolecular forces between the molecules of the same compound.

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Answer:

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