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kodGreya [7K]
2 years ago
10

Round off each of the following numbers to two significant figure 0.436 and 9.000

Chemistry
1 answer:
rodikova [14]2 years ago
6 0

Answer:

0.436 ⇒ 0.44

9.000 ⇒ 9.0

Concept:

<u>Significant figures</u> are where each of the digits of a number are used to express it to the required degree of accuracy, starting from the first nonzero digit.

Therefore, in the context of this question, two significant figure means that <u>two digits of numbers are kept</u>, from left to right, starting from the first nonzero digit.

<u>Solve:</u>

<h2>PART I: Rounding 0.436</h2>

0.436 has <u>3 significant digits</u> in total starting from left to right

Thus, the last digit should be rounded up / down

Since the last digit is 6, <u>it is greater than 5</u>, so it should be rounded up.

Therefore, a rounded 0.436 is \Large\boxed{0.44}

<h2>PART II: Rounding 9.000</h2>

9.000 has 4 significant digits in total starting from left to right

Thus, the last two digits should be rounded up / down

Since the last two digits are 0, <u>it is less than 5</u>, so it should be rounded up (or remained).

Therefore, a rounded 9.000 is \Large\boxed{9.0}

Hope this helps!! :)

Please let me know if you have any questions

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Your question is not complete as you have omitted some significant values in the question. Please let me assume this to be your question;

QUESTION;

Understanding the enthalpy definition=

Measurements show that the enthalpy of a mixture of gaseous reactants increases by 125.kJ during a certain chemical reaction, which is carried out at a constant pressure. Furthermore, by carefully monitoring the volume change it is determined that -71.kJ of work is done on the mixture during the reaction. Calculate the change in enthalpy of the gas mixture during the reaction and determine if the reaction is endothermic or exothermic.

ANSWER: The change in enthalpy of the gas mixture during the reaction is 54.kJ

The reaction is endothermic.

EXPLANATION: Enthalpy is the heat change in a system.

To calculate enthalpy we use the formula below;

H = E + PV

H is the enthalpy

E is the energy used in the reaction

PV is the product of pressure and volume which is refered to as the work done in the system

Using the equation above

H = 125 + (-71) = 54.kJ

An endothermic reaction is a type of reaction where heat is gained by the system from it's environment, and the enthalpy of such system is positive. While an Exothermic reaction is a type of reaction where heat is lost by the system to it's environment, and the enthalpy of such system is negative.

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<h3>Empirical formula calculation</h3>

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H = 15/201.6 = 7.44% = 7.44/1 = 7.44 moles

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Divide the number of moles by the smallest"

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Thus, the empirical formula is NH_4Cl

More on empirical formula can be found here: brainly.com/question/14044066

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