a) synthesis- or combination- reaction
The chemical reaction would be expressed as follows:
HBr + LiOH = LiBr + H2O
We are given the volumes and corresponding concentration to be used for the reaction. We use these values to solve for the concentration of the other reactant. We do as follows:
0.253 mol LiOH / L solution ( 0.01673 L ) ( 1 mol HBr / 1 mol LiOH ) = 0.00423 HBr needed
Concentration of HBr =0.00423mol / .010 L = 0.423 M HBr
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Answer:
B) 82 protons
Explanation:
The number of protons for an element never change. 82 Is the atomic number for Pb which is how many protons it has. An isotope means it has more neutrons.
Taking into account the scientific notation, the result of the subtraction is 6.5×10⁵.
<h3>Scientific notation</h3>
First, remember that scientific notation is a quick way to represent a number using powers of base ten.
The numbers are written as a product:
a×10ⁿ
where:
- a is a real number greater than or equal to 1 and less than 10, to which a decimal point is added after the first digit if it is a non-integer number.
- n is an integer, which is called an exponent or an order of magnitude. Represents the number of times the comma is shifted. It is always an integer, positive if it is shifted to the left, negative if it is shifted to the right.
<h3 /><h3>Subtraction in scientific notation</h3>
You want to subtract two numbers in scientific notation. It should be noted that when the numbers to be added do not have the same base 10 exponent, the base 10 power with the highest exponent must be found. In this case, the highest exponent is 5.
Then all the values are expressed as a function of the base 10 exponent with the highest exponent. In this case: 5.00×10⁴=0.500×10⁵
Taking the quantities to the same exponent, all you have to do is subtract what was previously called the number "a". In this case:
7.00×10⁵ - 0.500×10⁵= (7.00- 0.500)×10⁵= 6.5×10⁵
Finally, the result of the subtraction is 6.5×10⁵.
Learn more about scientific notation:
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