A. 4 mm.......0.5 mm
B. 1.5 mm......same size
Answer:

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.

Multiply by the given number of grams.

Flip the ratio so the grams of sodium oxide can cancel each other out.




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.

There are <u>2.48 moles of sodium oxide</u> in 154 grams, so choice A is correct.
<u>Answer:</u> The number of atoms of carbon present in given number of moles are 
<u>Explanation:</u>
We are given:
Number of moles of carbon = 
According to mole concept:
1 mole of an element contains
number of atoms.
So,
of carbon will contain =
number of atoms.
Hence, the number of atoms of carbon present in given number of moles are 
net ionic equation
B) SO₄²⁻ (aq) + Ba²⁺ (aq) → BaSO₄ (s)
Explanation:
We have the following chemical equation:
2 Na⁺ (aq) + SO₄²⁻ (aq) + Ba²⁺ (aq) + 2 Cl⁻ (aq) → 2 Na⁺ (aq) + 2 Cl⁻ (aq) + BaSO₄ (s)
To get the net ionic equation we remove the spectator ions and we get:
SO₄²⁻ (aq) + Ba²⁺ (aq) → BaSO₄ (s)
were:
(aq) - aqueous
(s) - solid
Learn more about:
net ionic equation
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