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3 years ago

Boron (B) has two isotopes, boron-10 and boron-11. The atomic weight of boron is ?

Chemistry

1 answer:

suter [353]3 years ago

8 0

Answer:

Approximately 10,5

Explanation:

The question is not really very specific, because it would need the percentages of those isotopes in the nature. As they are not shown, it should be the median of those two numbers.

atomic weight ≈ $\frac{10+11}{2}$ = 10,5

If you check a periodic table, you'll see it's actually 10,8, but that's because of the thing I told you at first (percentages missing).

Hope I could help.

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Ana amount of nitrogen undergoes a physical change and increases its volume. What can be known about this physical change

Natali [406]

Answer:

D.) the density changed

Explanation:

This would be the answer because it is a specific amount of Nitrogen undergoing a physical change. Since the color and boiling point don't influence a change in volume, those are ruled out. Also, nitrogen's molecular mass never changes, so that would not make sense either. But if the density, which is mass/volume, has changed (more specifically decreases) then it means the volume has increased.

Hope this helps.

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3 years ago

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What is the surface area of the triangular prism?<br> 60ft<br> 72ft<br> 82ft<br> 84ft

ch4aika [34]

Answer: I’m pretty sure it’s 60

Explanation:

3 0

3 years ago

Ethanol melts at -114 degree C. The enthalpy of fusion

Brut [27]

Answer: The heat required is 6.88 kJ.

Explanation:

The conversions involved in this process are :

$(1):ethanol(s)(-135^0C)\rightarrow ethanol(s)(-114^0C)\\\\(2):ethanol(s)(-114^0C)\rightarrow ethanol(l)(-114^0C)\\\\(3):ethanol(l)(-114^0C)\rightarrow ethanol(l)(-50^0C)$

Now we have to calculate the enthalpy change.

$\Delta H=[m\times c_{p,s}\times (T_{final}-T_{initial})]+n\times \Delta H_{fusion}+[m\times c_{p,l}\times (T_{final}-T_{initial})]+n\times \Delta H_{vap}+[m\times c_{p,g}\times (T_{final}-T_{initial})]$

where,

$\Delta H$ = enthalpy change = ?

m = mass of ethanol = 25.0 g

$c_{p,s}$ = specific heat of solid ethanol= 0.97 J/gK

$c_{p,l}$ = specific heat of liquid ethanol = 2.31 J/gK

n = number of moles of ethanol = $\frac{\text{Mass of ethanol}}{\text{Molar mass of ethanol}}=\frac{25.0g}{46g/mole}=0.543mole$

$\Delta H_{fusion}$ = enthalpy change for fusion = 5.02 KJ/mole = 5020 J/mole

$T_{final}-T_{initial}=\Delta T$ = change in temperature

The value of change in temperature always same in Kelvin and degree Celsius.

Now put all the given values in the above expression, we get

$\Delta H=[25.0 g\times 0.97J/gK\times (-114-(-135)K]+0.534mole\times 5020J/mole+[25.0g\times 2.31J/gK\times (-50-(-114))K]$

$\Delta H=6885.93J=6.88kJ$ (1 KJ = 1000 J)

Therefore, the heat required is 6.88 kJ

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3 years ago

What is the best way to get rid of a headache?

ryzh [129]

Drink lots of water and pain medication

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3 years ago

An acid solution contains more... ions than... ions.

spayn [35]

Answer: An acid contains more hydrogen ions than hydroxide ions.

Explanation:

An acid is defined as the chemical compound which has a high concentration of hydrogen ions. They are considered as proton donors and they act as proton $(H^+)$ donors when they have high concentration of hydrogen ions.

A base is defined as a chemical substance which has high concentration of hydroxide ions. They are considered as proton acceptors and they act as proton $(H^+)$ acceptors when they have low concentration of hydrogen ions.

Hence, an acid is contains more hydrogen ions than hydroxide ions.

4 0

3 years ago