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3 years ago

5) Why do elements in the same family generally have similar properties?

1 answer:

4 0

Answer: Elements in the same family generally have similar properties because they contain the same number of the electrons, for instance.

Hope this helped!

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Which salt is produced by the neutralization of sodium hydroxide with sulfuric acid?

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NaOH+H2SO4=NAHSO4+H2O

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In some parts of the galaxy, electrons in hot hydrogen gas may be excited to very high quantum levels. Calculate the wavelength

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In some parts of the galaxy, electrons in hot hydrogen gas may be excited to very high quantum levels. Calculate the wavelength of light that would be emitted if electrons moved from the ð‘›=10 shell to the ð‘›=2 shell Î»=___nm

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A factor that keeps a population size from growing too large is called a ______ _______.

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3 years ago

Read 2 more answers

Pentaborane−9 (B5H9) is a colorless, highly reactive liquid that will burst into flames when exposed to oxygen. The reaction is

mote1985 [20]

Answer : The heat released per gram of the compound reacted with oxygen is 71.915 kJ/g

Explanation :

Enthalpy change : It is defined as the difference in enthalpies of all the product and the reactants each multiplied with their respective number of moles. It is represented as $\Delta H^o$

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 equilibrium reaction follows:

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

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

$\Delta H^o_{rxn}=[(n_{(B_2O_3)}\times \Delta H^o_f_{(B_2O_3)})+(n_{(H_2O)}\times \Delta H^o_f_{(H_2O)})]-[(n_{(B_5H_9)}\times \Delta H^o_f_{(B_5H_9)})+(n_{(O_2)}\times \Delta H^o_f_{(O_2)})]$

We are given:

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

Putting values in above equation, we get:

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

Now we have to calculate the heat released per gram of the compound reacted with oxygen.

From the reaction we conclude that,

As, 2 moles of compound released heat = -9078.57 kJ

So, 1 moles of compound released heat = $\frac{-9078.57}{2}=-4539.28kJ$

For per gram of compound:

Molar mass of $B_5H_9$ = 63.12 g/mole

$\Delta H^o_{rxn}=\frac{-4539.28}{63.12}=-71.915kJ/g$

Therefore, the heat released per gram of the compound reacted with oxygen is 71.915 kJ/g

7 0

3 years ago

a regular solid has a length of 28cm. , a width of 16cm. and a total surface area of 1424cm squared. What is the total surface a

Brrunno [24]

Answer:

A = 356 cm²

Explanation:

In this case, you need to use the formula to calculate the area of regular solid.

This is the following expression:

S = 2LH + 2LW + 2WH

Where:

L: length

W: Width

H: Height

But we do not know the height of the solid. We should calculate it with the given data first:

1424 = 2*28*H + 2*28*16 + 2*16*H

1424 = 56H + 896 + 32H

1424 - 896 = 88H

H = 528/88

H = 6 cm

Now that we know the height we can calculate the area of the other solid. In the other solid the length has been reduced to half, so I will assume that the Width and height is also reduced to half.

L2 = 14 cm

W2 = 8 cm

H2 = 3 cm

Replacing we have:

S = (2*14*3) + (2*14*8) + (2*8*3)

S = 356 cm²

And this should be the total surface area, assuming the width and height is reduced to half too.

If you don't assume it's reduced to half, then use the original values of Width and Height. Doing so, the Surface would be:

S = (2*14*6) + (2*14*16) + (2*6*16)

S = 808 cm²

5 0

3 years ago