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3 years ago

What is the mass number of the atom shown? a. 11 b. 18 d. 20 C. 19

Chemistry

2 answers:

PolarNik [594]3 years ago

6 0

Answer:

Explanation:it is 11

Anastasy [175]3 years ago

6 0

It is 20 because the mass is proton + neutron!!! hope this helped :)

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This is a type of element that has many valence electrons, not a conductor.

cestrela7 [59]

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Are specimens the best source of DNA

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3 years ago

Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction:P4(g) + 10 Cl2(g) → 4PCl5(s) ΔH°

miskamm [114]

Answer: The $\Delta H^o_{rxn}$ for the reaction is -1835 kJ.

Explanation:

Hess’s law of constant heat summation states that the amount of heat absorbed or evolved in a given chemical equation remains the same whether the process occurs in one step or several steps.

According to this law, the chemical equation is treated as ordinary algebraic expressions and can be added or subtracted to yield the required equation. This means that the enthalpy change of the overall reaction is equal to the sum of the enthalpy changes of the intermediate reactions.

The given chemical reaction follows:

$P_4(g)+10Cl_2(g)\rightarrow 4PCl_5(s)$ $\Delta H^o_{rxn}=?$

The intermediate balanced chemical reaction are:

(1) $PCl_5(s)\rightarrow PCl_3(g)+Cl_2(g)$ $\Delta H_1=157kJ$ ( × 4)

(2) $P_4(g)+6Cl_2(g)\rightarrow 4PCl_3(g)$ $\Delta H_2=-1207kJ$

The expression for enthalpy of the reaction follows:

$\Delta H^o_{rxn}=[4\times (-\Delta H_1)]+[1\times \Delta H_2]$

Putting values in above equation, we get:

$\Delta H^o_{rxn}=[(4\times (-157))+(1\times (-1207))=-1835kJ$

Hence, the $\Delta H^o_{rxn}$ for the reaction is -1835 kJ.

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3 years ago

Michelle has a beaker containing NaCl. What is in Michelle's beaker

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3 years ago

Read 2 more answers

An atom of an element has 54 protons. Some of the elements atoms have 77 neutrons, while other atoms have 79 neutrons. What are

Alja [10]

Answer:

The atomic numbers of both are 54 while the mass numbers are 131 and 133 respectively.

Explanation:

- The number of protons = Atomic number. So, if the atom has 54 protons and it remained unchanged, then the two types of atoms of this element both have atomic numbers of 54.

- On the other hand, mass number is the sum of protons and neutrons

So, if type 1 has protons = 54 and neutrons = 77: mass number = 54 + 77 = 131

if Type 2 has protons = 54 and neutrons = 79: mass number = 54 + 77 = 133

(Since the possibility of atoms of the same element to have different mass numbers but the same atomic number is called isotopy). The two types of atoms with mass numbers 131 and 133 described are isotopes.

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3 years ago