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3 years ago

Which of the following reasons best describes the need for standards of measurement?

Chemistry

1 answer:

postnew [5]3 years ago

3 0

Before standards of measurement, measurements of the same kind would differ from person to person.

Answer:

The correct option would be the third one which says measurements differed from person to person.

Explanation:

There was a need to change the standard of measurement because earlier body parts be used for measuring certain quantity. But since the body parts have different sizes and shapes for different people the measurement of quantity would also differ from one person to another person.

Hence this difference in quantity for different people was the reason for the need of new standards of measurement.

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What is the MOST accurate conclusion can you draw about the vaporization of the substance?

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It requires much more energy to vaporize the substance than to melt it

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12 POINTS!!!! Consider the diagram. Which postulate of the kinetic-molecular theory best describes the event in the diagram?

podryga [215]

The separation of molecules. I wouldn't put that if i were you.

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How many elements are identified in tearms of their atoms

lianna [129]

their identified by the number of protons they have in the nucleus which = their electrons.

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4 years ago

(LO 3N, 4G, 4O) Aluminum sulfate is also involved in dying fabrics. The gelatinous precipitate formed in the reaction with dilut

brilliants [131]

9.4 × 10⁻³ mg (0.73 mmoles) of Al(OH)₃ is formed

Explanation:

We have the following chemical reaction:

Al₂(SO₄)₃(aq) + 6 NaOH(aq) → 2 Al(OH)₃(s) + 3 Na₂SO₄(aq)

The precipitate mentioned by the problem is aluminium hydroxide Al(OH)₃.

Now to determine the number of moles of sodium hydroxide NaOH we use the following formula:

molar concentration = number of moles / volume

number of moles = molar concentration × volume

number of moles of NaOH = 0.088 M × 25 mL = 2.2 mmoles

number of moles of Al₂(SO₄)₃ = 5.6 × 10⁻³ moles = 5.6 mmoles (found in the problem text)

We see from the chemical reaction that 1 mole of Al₂(SO₄)₃ requires 6 moles of NaOH so 5.6 mmoles of Al₂(SO₄)₃ would require 6 times more NaOH which is 33.6 mmoles and we have only 2.2 mmoles. The limiting reactant will be NaOH.

Now we devise the following reasoning:

if 6 mmoles of NaOH produces 2 mmoles of Al(OH)₃

then 2.2 mmoles of NaOH produces X mmoles of Al(OH)₃

X = (2.2 × 2) / 6 = 0.73 mmoles of Al(OH)₃

mass of Al(OH)₃ = number of moles / molecular weight

mass of Al(OH)₃ = 0.73 / 78

mass of Al(OH)₃ = 9.4 × 10⁻³ mg

Learn more:

precipitation reaction

brainly.com/question/10400269

7 0

3 years ago

The enthalpy of vaporization for water is 40.67 kJ/mol and the enthalpy of fusion for water is

S_A_V [24]

Answer:

$\Delta H_{dep}=-46.68kJ/mol$

Explanation:

Hello!

In this case, since vaporization is the processes by which a liquid goes to the gas phase, fusion by which a solid goes to liquid and deposition by which a gas goes to solid; we infer that the following set up relates the enthalpies associated to each process:

$\Delta H_{fus}+\Delta H_{vap}=-\Delta H_{dep}$

Because deposition goes from a state with more energy to a state with less energy, therefore it is negative; in such a way, by plugging in we obtain:

$\Delta H_{dep}=-(\Delta H_{fus}+\Delta H_{vap})\\\\\Delta H_{dep}=-(6.01kJ/mol+40.67kJ/mol)\\\\\Delta H_{dep}=-46.68kJ/mol$

Best regards!

6 0

3 years ago