Diatomic gases such as H2(g), O2(g), and N2(g) contain ________ bonds.
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The normal boiling point corresponds to the temperature at which both the liquid and gas are under the standard atmospheric pressure of 1 atm.TRUE FALSE
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 )
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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.
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
- 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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C2H5OH(l)+3O2(g)→2CO2(g)+3H2O(l), ΔH = –1367 kJ/mol
C(s)+O2(g)→CO2(g), ΔH = –393.5 kJ
H2(g)+½O2(g)→H2O(l), ΔH = –285.8 kJ
a. -277.6 kJ/mol
b. -194.7 kJ/mol
c. 194.7 kJ/mol
d. 486 kJ/mol
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Answer:
The answer is a. -277.6 kJ/mol
Explanation:
We have to arrange and sum the given equations to obtain the desired reaction as follows:
3 H₂O(l) + 2 CO₂(g) → 3 O₂(g) + C₂H₅OH(l) ΔH1= (-1) x (-1367 KJ/mol)
2 C(s) + 2 O₂(g)→ 2 CO₂(g) ΔH2= 2 x (-393.5 KJ/mol)
3 H₂(g) + 3/2 O₂(g) → 3 H₂O(l) ΔH3= 3 x (-285.8 KJ/mol)
In the first equation (ΔH1) , we multiply the enthalphy by (-1) because we use the reverse reaction. In the second and third equations (ΔH2 and ΔH3), we multiply by 2 and 3, respectively. Once we sum and cancel the terms that are repeated in both sides of the reactions, we obtain:
3H₂(g) + 2C(s) + ½O₂(g) → C₂H₅OH(l)
The total enthalphy is:
ΔH= ΔH1 + ΔH2 + ΔH3
ΔH= (-1) x (-1367 KJ/mol) + 2 x (-393.5 KJ/mol) + 3 x (-285.8 KJ/mol)
ΔH= -277.4 KJ/mol
The nearest answer between the given options is option a (-277.6 KJ/mol)
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It can save five times its purchase price in electricity cost because it contains toxic mercury that is equivalent in working: electrons that are bound to mercury atoms are excited to states where they will radiate ultraviolet light as they return to lower energy level, this ultraviolet light will be converted into visible light as it strikes to the coating of the bulb. Like LED that is high-efficiency house lighting.