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3 years ago

78.9 + 890.43 - 21 = 9.5 x 10^2

Chemistry

1 answer:

maria [59]3 years ago

8 0

948 or 9.48 x 10^2

There are two sets of rules for significant figures

• One set for addition and subtraction

• Another set for multiplication and division

You used the set for multiplication and division.

This problem involves addition and subtraction, and the rule is

The number of places after the decimal point in the answer must be <em>no greater than the number of decimal places in every term</em> in the sum.

Thus, we have

78.9

+890.43

-21.

= 948.33

The "21" term has the fewest digits after the decimal point (none), so the answer must have no digits after the decimal point.

To the correct answer is 948 = 9.48 x 10^2. It has three significant figures.

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Answer:

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Explanation:

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He used the prefix ''eka'' to refer to elements whose properties were alike but were yet to be discovered at that time.

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The forensic technician at a crime scene has just prepared a luminol stock solution by adding 18.0 g of luminol into a total vol

Paladinen [302]

Answer:

1.36M

Explanation:

Luminol is a compound having the molecular formula as C8H7N3O2.

To know the molarity of the stock solution of Luminol, we shall carry out the following:

Step 1:

we shall calculate the number of mole in 18g of luminol. This is shown below:

Molar mass of C8H7N3O2 = (12x8) + (7x1 ) + (14x3) + (16x2)

= 96 + 7 + 42 + 32

= 177g/mol

Mass of C8H7N3O2 = 18g

Number of mole of C8H7N3O2 =..?

Mole = Mass /Molar Mass

Number of mole of C8H7N3O2 = 18/177 = 0.102 mole.

Step 2:

Conversion of 75.0 mL of H2O to Litre (L).

1000mL = 1L

Therefore, 75mL = 75/1000 = 0.075L

Step 3:

Determination of the molarity of the stock solution of Luminol.

Molarity is simply defined as the mole of solute per unit litre of water. Mathematically, it is represented as:

Molarity = mole /Volume

With the above formula, we can obtain the molarity of the stock solution of Luminol as follow:

Mole of C8H7N3O2 = 0.102 mole

Volume of water = 0.075L

Molarity =..?

Molarity = mole /Volume

Molarity = 0.102/0.075

Molarity = 1.36M

Therefore, the molarity of the stock solution of Luminol is 1.36M.

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3 years ago