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SIZIF [17.4K]
3 years ago
12

An atom has a mass number of 31 and an atomic number of 15. How many protons and how many neutrons are in this atom? Show the nu

clear symbol for this atom.

Chemistry
1 answer:
vaieri [72.5K]3 years ago
5 0
The atomic number of an atom is equal to the amount of protons the atom has, and the mass number is equal to the sum of the protons and neutrons. Therefore:

let protons = p
let neutrons = n                                                  
let atomic mass = a

P+N=A 
15+n=31
n=16

There are 16 neutrons in this atom.
(See attached for nuclear symbol)

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Given the following heats of combustion. CH3OH(l) + 3/2 O2(g) CO2(g) + 2 H2O(l) ΔH°rxn = -726.4 kJ C(graphite) + O2(g) CO2(g) ΔH
sergeinik [125]

Answer:

The standard enthalpy of formation of methanol is, -238.7 kJ/mole

Explanation:

The formation reaction of CH_3OH will be,

C(s)+2H_2(g)+\frac{1}{2}O_2\rightarrow CH_3OH(g),\Delta H_{formation}=?

The intermediate balanced chemical reaction will be,

C(graphite)+O_2(g)\rightarrow CO_2(g), \Delta H_1=-393.5kJ/mole..[1]

H_2(g)+\frac{1}{2}O_2(g)\rightarrow H_2O(l), \Delta H_2=-285.8kJ/mole..[2]

CH_3OH(g)+\frac{3}{2}O_2(g)\rightarrow CO_2(g)+2H_2O(l) , \Delta H_3=-726.4kJ/mole..[3]

Now we will reverse the reaction 3, multiply reaction 2 by 2  then adding all the equations, Using Hess's law:

We get :

C(graphite)+O_2(g)\rightarrow CO_2(g) , \Delta H_1=-393.5kJ/mole..[1]

2H_2(g)+2O_2(g)\rightarrow 2H_2O(l) ,\Delta H_2=2\times (-285.8kJ/mole)=-571.6kJ/mol..[2]

CO_2(g)+2H_2O(l)\rightarrow CH_3OH(g)+\frac{3}{2}O_2(g) ,\Delta H_3=726.4kJ/mole [3]

The expression for enthalpy of formation of C_2H_4 will be,

\Delta H_{formation}=\Delta H_1+2\times \Delta H_2+\Delta H_3

\Delta H=(-393.5kJ/mole)+(-571.6kJ/mole)+(726.4kJ/mole)

\Delta H=-238.7kJ/mole

The standard enthalpy of formation of methanol is, -238.7 kJ/mole

4 0
3 years ago
In sexual reproduction, two individuals produce offspring that have genetic characteristics from both parents. This type of repr
agasfer [191]

Answer:

genetic variation

Explanation:

7 0
3 years ago
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The isotope 106 46Pd (106 on top and 46 on bottom)
vazorg [7]

Answer:

4. 60 neutrons.

Explanation:

The given isotopes;

         ¹⁰⁶₄₆Pd

In this isotope, we can deduce that the mass number is the superscript and the atomic number is the subscript;

     Mass number  = 106

     Atomic number  = 46

Mass number is the number of protons and neutrons in an atom;

       Mass number = Protons + neutrons

Atomic number is the number of protons

   

So,  Number of protons  = 46

Number of neutrons  = Mass number  - Atomic number

                                    = 106  - 46

                                     = 60

Number of neutrons  = 60

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Answer:

The volume of an irregularly shaped solid can be determined from the volume of water it displaces. A graduated cylinder contains 19.9 mL of water. When a small piece of galena is added, it sinks and the volume increases to 24.5 mL

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