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2 years ago

Write the nuclear symbol for the neutral atom shown. 5 protons, 6 neutrons, 5 electrons. nuclear symbol:

Chemistry

1 answer:

OLga [1]2 years ago

3 0

Answer:

Explanation:

the element is boron, therefore B is the symbol

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Pentaborane-9, B5H9, is a colorless, highly reactive liquid that will burst into flame when exposed to oxygen. The reaction is 2

mina [271]

Answer: The amount of energy released per gram of $B_5H_9$ is -71.92 kJ

Explanation:

For the given chemical reaction:

$2B_5H_9(l)+12O_2(g)\rightarrow 5B_2O_3(s)+9H_2O(l)$

The equation used to calculate enthalpy change is of a reaction is:

$\Delta H^o_{rxn}=\sum [n\times \Delta H^o_f_{(product)}]-\sum [n\times \Delta H^o_f_{(reactant)}]$

The equation for the enthalpy change of the above reaction is:

$\Delta H^o_{rxn}=[(5\times \Delta H^o_f_{(B_2O_3(s))})+(9\times \Delta H^o_f_{(H_2O(l))})]-[(2\times \Delta H^o_f_{(B_5H_9(l))})+(12\times \Delta H^o_f_{(O_2(g))})]$

Taking the standard enthalpy of formation:

$\Delta H^o_f_{(B_2O_3(s))}=-1271.94kJ/mol\\\Delta H^o_f_{(H_2O(l))}=-285.83kJ/mol\\\Delta H^o_f_{(B_5H_9(l))}=73.2kJ/mol\\\Delta H^o_f_{(O_2(g))}=0kJ/mol$

Putting values in above equation, we get:

$\Delta H^o_{rxn}=[(5\times (1271.94))+(9\times (-285.83))]-[(2\times (73.2))+(12\times (0))]\\\\\Delta H^o_{rxn}=-9078.57kJ$

We know that:

Molar mass of pentaborane -9 = 63.12 g/mol

By Stoichiometry of the reaction:

If 2 moles of $B_5H_9$ produces -9078.57 kJ of energy.

Or,

If $(2\times 63.12)g$ of $B_5H_9$ produces -9078.57 kJ of energy

Then, 1 gram of $B_5H_9$ will produce = $\frac{-9078.57kJ}{(2\times 63.12)}\times 1g=-71.92kJ$ of energy.

Hence, the amount of energy released per gram of $B_5H_9$ is -71.92 kJ

8 0

3 years ago

If you want to lift a 30-kg box to a height of 1 m, how much work will it take?

natta225 [31]

Explanation:

workdone = force x distance

force = mass x acceleration

30 x 10 = 300N

300N x 1m

workdone= 300J

7 0

3 years ago

(a) Red light has a wavelength of roughly 700 nm. What is the wavelength in m? ball park 10.10' (b) What is the wavelength of re

joja [24]

Explanation:

a) Wavelength of red light = 700 nm

1 nanometer = $10^{-9} meter$

Wavelength of red light in meter will be:

$=700 nm=700\times 10^{-9} m=7.00\times 10^{-7} m$

b) Wavelength of red light = $7.00\times 10^{-7} m$

1 meter = 39.3701 inches

Wavelength of red light in inches will be:

$7.00\times 10^{-7} m=7.00\times 10^{-7}\times 39.3701 inches$

$=2.7559\times 10^{-5} inches$

Value of distance given = 90.123 km

1 km = 3280.84 feet

$90.123 km=90.123 \times 3280.84 feet=295,679.1433 feet$

1 foot = 0.1515152 chain

$295,679.1433 feet=295,679.1433\times 0.1515152 chain$

$=44,799.88453 feet\approx 4.48\times 10^4 chains$

Value of distance in chains:

$90.123 km=4.48\times 10^4 chains$

3 0

3 years ago

A 360. mg sample of aspirin, C9H8O4, (molar mass 180. g), is dissolved in enough water to produce 200. mL of solution. What is t

Gemiola [76]

Answer:

Molarity = 0.01 M

Explanation:

Molarity is used to measure the concentration of a solution. It will be same for the whole solution or a small amount of solution if the solution is homogeneous.

So, Molarity of 200 mL of solution = Molarity of 50 mL of solution

$\mathbf{Molarity = \frac{number \ of \ moles \ of \ solute}{Volume \ of \ solution \ (in \ liters)}}$