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3 years ago

Pls answer

Chemistry

1 answer:

vlabodo [156]3 years ago

3 0

Answer:

The law of conservation of mass was obeyed since some of the mass evaporated while the cookies were baking.

Explanation:

The law of conservation of mass, as other physic's laws, is universal, meaning that it is obeyed in any circumstance, place, and time.

Thus, any explanation that asserts that the law of conservation of mass is not obeyed must be discarded.

Hence, first, second and fourth options are incorrect.

The law of conservation of mass states that during any physical or chemical process the mass of the substances can neither created nor destroyed; then, what happened that made the mass of the mixture of ingredients mixed by Maria (1053 g) were greater than the mass of the cookies baked for 15 minutes (845 g)?

One of the physical process that occurs when cooking, due to the increase of temperature, is the evaporation of water (besides the chemical reactions between the ingredients, some of which produce other gases).

The water in form of vapor (steam) will "escape" from the mass and the oven, so when the cookies are weighted they will weight less than the mixture, because the water was transformed from liquid state to gas state; i.e. some of the mass evaporated while the cookies were baking. Thus, the third choice is correct.

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Which of the following is an example of a covalent bond?

loris [4]

Answer:

C. H2O

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4 0

3 years ago

. How many milliliters of 0.20 M HCl are needed to exactly neutralize 40. milliliters of 0.40 M KOH

Anuta_ua [19.1K]

Answer:

$V_{HCl}=80mL$

Explanation:

Hello,

In this case, for the given reactants we identify the following chemical reaction:

$KOH+HCl\rightarrow KCl+H_2O$

Thus, we evidence a 1:1 molar ratio between KOH and HCl, therefore, for the complete neutralization we have equal number of moles, that in terms of molarities and volumes become:

$n_{HCl}=n_{KOH}\\\\M_{HCl}V_{HCl}=M_{KOH}V_{KOH}$

Hence, we compute the volume of HCl as shown below:

$V_{HCl}=\frac{M_{KOH}V_{KOH}}{M_{HCl}} =\frac{0.40M*40mL}{0.20M} \\\\V_{HCl}=80mL$

Best regards.

5 0

3 years ago

Calculate the theoretical yield of aspirin obtained when 2.0 g of salicylic acid and 5.0 mL of acetic anhydride (density = 1.08

saw5 [17]

Answer:

The percent yield would be 73%

Explanation:

The balanced reaction for the obtention of acetylsalicylic acid (aspirin) is the following:

Salicylic acid + acetic anhydride → acetylsalicylic acid + acetic acid

C₇H₆O₃ + C₄H₆O₃ → C₉H₈O₄ + C₂H₄O₂

According to the reaction, 1 mol of salicylic acid reacts with 1 mol of acetic anhydride to give 1 mol of acetylsalicylic acid (aspirin) and 1 mol of acetic acid.

1 mol aspirin (C₉H₈O₄) = (9 x 12 g/mol) + (8 x 1 g/mol) + (4 x 16 g/mol)

= 180 g

1 mol salicylic acid (C₇H₆O₃) = (7 x 12 g/mol) + (6 x 1 g/mol) + (3 x 16 g/mol)

= 138 g

1 mol acetic anhydride (C₄H₆O₃) = (4 x 12 g/mol) + (6 x 1 g/mol) + (3 x 16 g/mol)

= 102 g

The stoichiometric ratio is = 138 g salicylic acid/102 g acetic anhydride= 1.35

We have:

2.0 g salicylic acid

acetic anhydride = 5.0 mL x 1.08 g/mL = 5.4 g

The reactants ratio is = 2.0 g salicylic acid/5.4 g acetic anhydride = 0.37

0.37 < 1.35 , therefore salicylic acid is the limiting reactant.

Now, we use the amount of salicylic acid to calculate the theoretical amount of aspirin. For this, we know that 1 mol of aspirin (180 g) is obtained from 1 mol of salycilic acid (138 g):

theoretical yield= 180 g aspirin/138 g salycilic acid x 2.0 g salycilic acid = 2.61 g aspirin

actual yield = 1.9 g

Finally, we calculate the yield:

percent yield = actual yield/theoretical yield x 100

= 1.9 g/2.6 g x 100 = 72.8% ≅ 73%

6 0

2 years ago

A chemist forms 16.6 g of potassium iodide by combining 3.9 g of potassium with 12.7 g of iodine. Show that these results are co

bezimeni [28]

3.9 g + 12.7 g = 16.6 g

The sum of the masses of potassium and iodine equals the mass of the product, potassium iodide. The results are consistent with he law of conservation of mass.

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3 0

3 years ago

How could you verify that you produced carbon dioxide in your combustion reaction? 2. what indication did you have that nh3 was

DanielleElmas [232]

1) Carbon dioxide is a gas, so when $CO_{2}$ is evolved in the reaction, it appears as bubbles. The gas released extinguishes the fire and it can turn lime water milky.

$Ca(OH)_{2} (aq) + CO_{2}(g) ----> CaCO_{3}(s) +H_{2}O(l)$

2) When $NH_{3}$ is released in a decomposition reaction we can identify by the strong pungent smell of the gas released.

3) Saturated citric acid can cause corrosion of the metal layers present in the pipes. So, before draining out any acid it is neutralized so that the pipes and other plumbing works do not get damaged leading to leaks in the drainage system.

5 0

3 years ago