<span>Avogadro's number.
1 mole of any substance, molecule or element is equal to a certain amount of atom.
6.022 x 10^23 is the Avogradro's constant.
Magnesium Oxide is a compound. therefore if you have 30.3 g of it (1 mol), it will have the same number of atoms.
34.69 moles of MgO has 208.9 x 10^23 number of atoms.
2.089 x 10^25 is also a correct answer.</span><span>
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We need to measure 20.0 grams of CaCl₂ to prepare 500 mL of 0.360 M solution.
First, we need to determine the required moles of CaCl₂. We have 500 mL (0.500 L) of a 0.360 M solution (0.360 moles of CaCl₂ per liter of solution).

Then, we will convert 0.180 moles to grams using the molar mass of CaCl₂ (110.98 g/mol).

To prepare the solution, we weigh 20.0 g of CaCl₂ and add it to a beaker with enough distilled water to dissolve it. We stir it, heat it if necessary, and when we have a solution, we transfer it to a 500 mL flask and complete it to the mark with distilled water.
We need to measure 20.0 grams of CaCl₂ to prepare 500 mL of 0.360 M solution.
You can learn more about solutions here: brainly.com/question/2412491
The number that represents the coefficient on the product side of the chemical reaction,
is 7.
<h3>Coefficients of chemical equations</h3>
In equations representing chemical reactions, the coefficient of each reactant or product of a reaction is the number that comes on the left-hand side just before the chemical formula.
The coefficient of each species in a chemical reaction is obtainable when the equation of the reaction is balanced.
For example, in the following equation: 2A + B = 3C + D
The coefficients of A, B, C, and D are 2, 1, 3, and 1 respectively.
Applying this to the product side of a chemical reaction;
It means that the coefficient of the product is 7.
More on coefficients of chemical equations can be found here: brainly.com/question/28294176
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The answer is C. and D. water and aluminum