CHEMISTRY HIGH SCHOOL

Identify which one of these are exact numbers. (Can be more than 1) a. 2.54 cm ( the number of centimeters in exactly 1 in)
b. 56.00 s ( a time measured by a stopwatch)
c. 4 choices ( the number of choices in this list)
d. 3 lbs ( the weight of an object measured on a scale )

Answers

Answer 1
Answer:

Answer: a. 2.54 cm ( the number of centimeters in exactly 1 in) and c. 4 choices ( the number of choices in this list)


Justification:


1) a. 2.54 cm ( the number of centimeters in exactly 1 in)


Although the exact length of one inch has varied in the past, currently the inch is defined as exactly 2.54 cm, so this is an exact number.



b. 56.00 s ( a time measured by a stopwatch)


The time measured by a stopwatch is not an exact number. The number is limited by the precision of the instrument (the stopwatch) and it migh have been 56.004 instead of 56.00, and the stopwatch cannot shoe that. So, this is not an exact number.


c. 4 choices ( the number of choices in this list)


This is, indeed an exact number. It is 4, not 4.1, nor 3.9, nor any other number.


d. 3 lbs ( the weight of an object measured on a scale )


As reasoned with the stopwatch, this measure, 3 lbs, is subject to the precision of the scale. It is not an exact number. It could be other number close to 3: 2.99 for example.
Answer 2
Answer:

These are exact numbers: c. 4 choices ( the number of choices in this list)  and d. 3 lbs ( the weight of an object measured on a scale )

Further explanation

The exact number is a value that is known with complete certainty. Examples are counted numbers of objects or certain unit conversions such as exactly 3 feet in 1 yard. Another example is, a dozen is defined as 12 objects, and a pound is defined as 16 ounces.

Fraction an exact number is a fraction takes two integers and places them in a ratio, for example 3/4 or 10/15. A decimal can express the same numerical quantity, but it does so with a single number (like 0.75 or 0.66). So, the fraction makes the relationship among numbers clear in the way it is written.

While a decimal can express the same numerical quantity, but it does so with a single number (like 0.75 or 0.66).

a. 2.54 cm ( the number of centimeters in exactly 1 in) is decimal

b. 56.00 s ( a time measured by a stopwatch)  is not exact numbers

c. 4 choices ( the number of choices in this list)  is exact numbers

d. 3 lbs ( the weight of an object measured on a scale ) is exact numbers

Learn more

  1. Learn more about exact number brainly.com/question/1847531

Answer details

Grade:  9

Subject:  chemistry

Chapter:  exact number

Keywords: exact number

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a. Sodium iodide: NaI
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How many grams are in 2.3 x 10^-4 moles of Ca3(PO4)2

Answers

Molar mass 

Ca₃(PO₄)₂ = 310 g/mol

1 mole -------------------> 310 g
2.3x10⁻⁴ mole ---------> ?

m = 2.3x10⁻⁴ * 310 / 1

m = 0.0713 g 

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Answers

Given four acids with different Ka's, the strongest acid will be the one with the greatest Ka. This can be verified by taking the -log(Ka). Larger Ka will result to less pH which means it becomes more acidic. Less Ka means it is relatively basic compared to others.

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What is the pressure in atm exerted by 2.48 moles of a gas in a 250.0 ml container at 58c?

Answers

Explanation:

The given data is as follows.

     V = 250.0 ml,                  T = 58^{o}C = 58 + 273 = 331 K

      n = 2.48 moles,              P = ?    ,             R = 0.082 atm L /K mol

Therefore, calculate the pressure using ideal gas equation as follows.

                       PV = nRT

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                            = (2.48 mol * 0.082 atm L/K mol * 331 K)/(250.0 ml)

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Answers

Answer : The correct option is, 1s^22s^22p3

Explanation :

Electronic configuration : It is defined as the arrangement of the electrons of an atom in an atomic orbital.

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As we know that the number of electrons is equal to the number of atomic number.

The number of electrons present in nitrogen = 7

Thus, the electronic configuration of nitrogen is, 1s^22s^22p3

1s22s22p3 considering N is the third element in the 2nd P sublevel
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