Are you saying Santa invensted electricty...my childhood was a lie!!!!
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➷ Astrology: It hasn't shown any clear effectiveness in studies and doesn't have any scientific validity.
Aromatherapy with essential oils: It is only backed with low quality studies that just demonstrate the placebo effect
Acupuncture: Lots of research suggests it is just the placebo effect so it has no scientific backing
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➶ Hope This Helps You!
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↬ <u>ʜᴀɴɴᴀʜ</u> ♡
Answer is: 2) A positively charged nucleus is surrounded by mostly empty space.
Rutherford theorized that atoms have their charge concentrated in a very small nucleus.
This was famous Rutherford's Gold Foil Experiment: he bombarded thin foil of gold with positive alpha particles (helium atom particles, consist of two protons and two neutrons).
Rutherford observed the deflection of alpha particles on the photographic film and notice that most of alpha particles passed straight through foil.
That is different from Plum Pudding model, because it shows that most of the atom is empty space.
Answer:
![\boxed {\boxed {\sf A. \ 2.48 \ mol \ Na_2O}}](https://tex.z-dn.net/?f=%5Cboxed%20%7B%5Cboxed%20%7B%5Csf%20A.%20%5C%202.48%20%5C%20mol%20%5C%20Na_2O%7D%7D)
Explanation:
We are asked to convert an amount in grams to moles. To do this, we use the molar mass. This is the number of grams in one mole of a substance. It is the same value numerically as the atomic mass on the Periodic Table, however the units are grams per mole, not atomic mass units.
Look up the molar masses for the individual elements.
- Sodium (Na): 22.9897693 g/mol
- Oxygen (O): 15.999 g/mol
Look back at the formula: Na₂O. Notice there is a subscript of 2 after sodium. This means there are 2 atoms of sodium in every molecule, so we have to multiply sodium's molar mass by 2 before adding oxygen's.
- Na₂O: 2(22.9897693 g/mol)+ 15.999 g/mol = 61.9785386 g/mol
Set up a ratio using the molar mass.
![\frac {61.9785386 \ g \ Na_2O}{1 \ mol \ Na_2O}](https://tex.z-dn.net/?f=%5Cfrac%20%7B61.9785386%20%5C%20g%20%5C%20Na_2O%7D%7B1%20%5C%20mol%20%5C%20Na_2O%7D)
Multiply by the given number of grams.
![154 \ g \ Na_2O*\frac {61.9785386 \ g \ Na_2O}{1 \ mol \ Na_2O}](https://tex.z-dn.net/?f=154%20%5C%20g%20%5C%20Na_2O%2A%5Cfrac%20%7B61.9785386%20%5C%20g%20%5C%20Na_2O%7D%7B1%20%5C%20mol%20%5C%20Na_2O%7D)
Flip the ratio so the grams of sodium oxide can cancel each other out.
![154 \ g \ Na_2O*\frac {1 \ mol \ Na_2O}{61.9785386 \ g \ Na_2O}](https://tex.z-dn.net/?f=154%20%5C%20g%20%5C%20Na_2O%2A%5Cfrac%20%7B1%20%20%5C%20mol%20%5C%20Na_2O%7D%7B61.9785386%20%5C%20g%20%5C%20Na_2O%7D)
![154 *\frac {1 \ mol \ Na_2O}{61.9785386 }](https://tex.z-dn.net/?f=154%20%2A%5Cfrac%20%7B1%20%20%5C%20mol%20%5C%20Na_2O%7D%7B61.9785386%20%7D)
![\frac {154}{61.9785386 } \ mol \ Na_2O](https://tex.z-dn.net/?f=%5Cfrac%20%7B154%7D%7B61.9785386%20%7D%20%20%5C%20mol%20%5C%20Na_2O)
![2.48473106141 \ mol \ Na_2O](https://tex.z-dn.net/?f=2.48473106141%20%5C%20mol%20%5C%20Na_2O)
The original measurement of grams given has 3 significant figures, so our answer must have the same. For the number we calculated, that is the hundredth place.
The 4 in the thousandth place tells us to leave the 8.
![2.48 \ mol \ Na_2O](https://tex.z-dn.net/?f=2.48%20%5C%20mol%20%5C%20Na_2O)
There are <u>2.48 moles of sodium oxide</u> in 154 grams, so choice A is correct.