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3 years ago

How many neutrons does element X have if its atomic number is 25 and its mass number is 91?

Chemistry

1 answer:

elixir [45]3 years ago

4 0

Answer:

Explanation:

The number of neutrons is the atomic number (25) subtracted from the mass (91). So, 91 - 25 = 66.

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True or false water readily dissolves most polar compounds

morpeh [17]

The answer is false, I hope this helps.

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4 years ago

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The balanced combustion reaction for C6H6 is 2C6H6(l)+15O2(g)⟶12CO2(g)+6H2O(l)+6542 kJ If 8.600 g C6H6 is burned and the heat pr

jenyasd209 [6]

Answer : The final temperature of the water is, $22.5166^oC$

Explanation : Given,

Mass of benzene = 8.600 g

Molar mass of benzene = 78 g/mole

First we have to calculate the moles of benzene.

$\text{Moles of benzene}=\frac{\text{Mass of benzene}}{\text{Molar mass of benzene}}=\frac{8.600g}{78g/mol}=0.1103mole$

Now we have to calculate the energy of combustion.

The given balanced chemical reaction is:

$2C_6H_6(l)+15O_2(g)\rightarrow 12CO_2(g)+6H_2O(l)+6542 kJ$

According to reaction,

As, 2 moles of benzene gives 6542 kJ of energy on combustion.

So, 0.1103 mole of benzene gives $\frac{6542 kJ}{2}\times 0.1103=360.7913kJ$ of energy on combustion.

Now we have to calculate the final temperature of the water.

Formula used : $q_w=m_w\times c_w\times \Delta T=m_w\times c_w\times (T_{final}-T_{initial})$

where,

$q_w$ = heat released = 360.7913 kJ = 36079.13 J

$m_w$ = mass of water = 5691 g

$c_w$ = specific heat of water= $4.18J/g^oC$

$T_{final}$ = final temperature = ?

$T_{initial}$ = initial temperature = $21^oC$

Now put all the given values in the above formula, we get:

$36079.13J=5691g\times 4.18J/g^oC\times (T_{final}-21^oC)$

$T_{final}=22.5166^oC$

Therefore, the final temperature of the water is, $22.5166^oC$

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4 years ago

Maria and Carla were hiking when Maria tripped, fell, and sprained her ankle. Carla took out the first-aid kit and unwrapped a c

alukav5142 [94]

the answer is C

It is a chemical change because heat energy is absorbed and the pack gets colder. A change in temperature is a sign that a chemical reaction has taken place; increase in temperature is an exothermic reaction and decrease in temperature is an endothermic reaction. This is an endothermic chemical reaction.

6 0

3 years ago

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Convert 16 inches to feet

MrRa [10]

There is 12 inches in 1 foot.

Divide 16 with 12 to get feet

16/12 = ~1.33 (rounded)

1.33 is your answer

hope this helps

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4 years ago

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Complete the sentences to identify the trend in first ionization energies as one proceeds down the group 7A elements and explain

Harrizon [31]

Answer:

a)decrease

b)increase

c)smaller

d)smaller

Explanation:

Ionization energy decreases down the group due to increase in the atomic radius. The distance between the outermost electron and the nucleus increases hence the nuclear attraction for the outermost electrons become smaller and the ionization energy also become smaller as electrons are now easily removed from the outermost shell.

Hence the group of answer choices provided above.

3 0

4 years ago