Answer:

Explanation:
<u>1. Convert Atoms to Moles</u>
We must use Avogadro's Number: 6.022*10²³. This is the number of particles (atoms, molecules, ions, etc.) in 1 mole of a substance. In this case, the particles are atoms of helium. We can create a ratio.

Multiply by the given number of helium atoms.

Flip the fraction so the atoms of helium cancel.



<u>2. Convert Moles to Grams</u>
We must use the molar mass, which is found on the Periodic Table.
Use this as a ratio.

Multiply by the number of moles we calculated. The moles will then cancel.



<u>3. Round </u>
The original measurement has 3 significant figures (5, 5, and 0). Our answer must have the same. For the number we calculated, it is thousandth place. The 3 in the ten thousandth place tells us to leave the 5.

The mass is <u>0.365 grams of helium</u> so choice A is correct.
Answer:
South American
Explanation:
When you look at a map of plates, only South American forms a boundary with the African plate out of those specific plates
In balancing reactions, the number of atoms on each side should be of equal number. It is the most important rule in reactions. Also, we should know the correct substances involved in the reaction. We do as follows:
2K + MgBr2 = 2KBr + Mg
Answer:
Explanation:
A solubility curve is a graph of solubility, measured in g/100 g water, against temperature in °C. Solubility curves for more than one substance are often drawn on the same graph, allowing comparisons between substances
Answer:
24.87× 10²³ atoms of Ni
Explanation:
Given data:
Number of atoms of Ni= ?
Number of moles of Ni = 4.13 mol
Solution:
we will calculate the number of atoms of Ni by using Avogadro number.
It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.
The number 6.022 × 10²³ is called Avogadro number.
1 mole = 6.022 × 10²³ atoms
4.13 mol × 6.022 × 10²³ atoms /1 mol
24.87× 10²³ atoms of Ni