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2 years ago

Provide at least three reasons why friction is needed.

2 answers:

6 0

Friction occurs when two surfaces come into contact. Excess friction hinders movement, and it wastes energy. Friction refers to a force that opposes motion. It is important because it is applied in almost all life processes.

levacccp [35]2 years ago

4 0

Friction slides or rolls one object to another

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2 years ago

Which has the reverse chemical reaction as

Mazyrski [523]

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2 years ago

Convert the condensed structures to line angle formulas: 1. CH3CH2CH(CH3)CH2CH3 8. CH:COCH 9. CH3CH2OCH3 2. CH3CH2CH(CH2CH3)CH(C

kumpel [21]

Answer:

Attached in the photo.

Explanation:

Hello,

The answers in the attached photo. Just three things:

- In the second point a parenthesis is missing to properly understand the molecule (after the oxygen), nevertheless, I assumed it was an ether.

- In the sixth point, there's a missing hydrogen for it to be an ether as well.

- In the tenth point the second parenthesis is not clear, it seems there's a missing subscript, nevertheless I draw it assuming complete octates.

Best regards.

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2 years ago

How can you use evidence to determine if a change is physical or chemical?

irakobra [83]

Physical change is the color, shape stuff like that and chemical change is once it’s changed it can’t go back

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2 years ago

Read 2 more answers

Aspirin can be made in the laboratory by reacting acetic anhydride (C 4H 6O 3) with salicylic acid (C 7H 6O 3) to form aspirin (

Anastasy [175]

Answer: The percent yield of the aspirin is 77.5 %.

Explanation:

To calculate the mass of acetic anhydride, we use the equation:

$\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}$

Density of acetic anhydride = 1.08 g/mL

Volume of acetic anhydride = 2.80 mL

Putting values in above equation, we get:

$1.08g/mL=\frac{\text{Mass of acetic anhydride}}{2.80mL}\\\\\text{Mass of acetic anhydride}=(1.08g/mL\times 2.80mL)=3.024g$

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

For acetic anhydride:

Given mass of acetic anhydride = 3.024 g

Molar mass of acetic anhydride = 102.1 g/mol

Putting values in equation 1, we get:

$\text{Moles of acetic anhydride}=\frac{3.024g}{102.1g/mol}=0.0296mol$

For salicylic acid:

Given mass of salicylic acid = 1.24 g

Molar mass of salicylic acid = 138.12 g/mol

Putting values in equation 1, we get:

$\text{Moles of salicylic acid}=\frac{1.24g}{138.12g/mol}=0.0089mol$

The chemical equation for the combustion of hexane follows:

$C_4H_6O_3+C_7H_6O_3\rightarrow C_9H_8O_4+C_2H_4O_2$

By Stoichiometry of the reaction:

1 mole of salicylic acid reacts with 1 mole of acetic anhydride

So, 0.0089 moles of salicylic acid will react with = $\frac{1}{1}\times 0.0089=0.0089mol$ of acetic anhydride

As, given amount of acetic anhydride is more than the required amount. So, it is considered as an excess reagent.

Thus, salicylic acid is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

1 mole of salicylic acid produces 1 mole of aspirin

So, 0.0089 moles of salicylic acid will produce = $\frac{1}{1}\times 0.0089=0.0089moles$ of aspirin

Now, calculating the mass of aspirin from equation 1, we get:

Molar mass of aspirin = 180.16 g/mol

Moles of aspirin = 0.0089 moles

Putting values in equation 1, we get:

$0.0089mol=\frac{\text{Mass of aspirin}}{180.16g/mol}\\\\\text{Mass of aspirin}=(0.0089mol\times 180.16g/mol)=1.60g$

To calculate the percentage yield of aspirin, we use the equation:

$\%\text{ yield}=\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100$

Experimental yield of aspirin = 1.24 g

Theoretical yield of aspirin = 1.60 g

Putting values in above equation, we get:

$\%\text{ yield of aspirin}=\frac{1.24g}{1.60g}\times 100\\\\\% \text{yield of aspirin}=77.5\%$

Hence, the percent yield of the aspirin is 77.5 %.

7 0

2 years ago