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3 years ago

Which of the following laboratory procedures best illustrates the law of conservation of mass?

Chemistry

2 answers:

77julia77 [94]3 years ago

4 0

Answer is: Synthesizing 36 g of H2O plus leftover reactants by combining 4 g of H2 and 32 g of O2.

m(H₂) + m(O₂) = m(H₂O).

4 g + 32 g = 36 g.

Conservation of mass: during chemical reaction no particles are created or destroyed, the atoms are rearranged from the reactants to the products.

Balanced chemical reaction: 2H₂ + O₂ → 2H₂O.

m(H₂) = 4 g; mass of hydrogen.

n(H₂) = 4 g ÷ 2 g/mol.

n(H₂) = 2 mol; amount of hydrogen.

m(O₂) = 32 g.

n(O₂) = 32 g ÷ 32 g/mol.

n(O₂) = 1 mol; amount of oxygen.

n(H₂) : n(O₂) = 2 mol : 1 mol according to balanced chemical reaction.

zavuch27 [327]3 years ago

4 0

Synthesizing 36 g of H2O because the mass of the reactants add up to the mass of the product

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Aspirin can be prepared from salicylic acid ( C 7 H 6 O 3 CX7HX6OX3), which has a molar mass of 138.12 g/mol, and acetic anhydri

pychu [463]

Answer: The theoretical yield of aspirin is 4.14 g

Explanation:

To calculate the moles :

$\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}$ $\text{Moles of salicylic acid}=\frac{3.20g}{138.12g/mol}=0.023moles$

mass of acetic anhydride = $density\times volume =1.082g/ml\times 3.71ml=4.01g$

$\text{Moles of acetic anhydride}=\frac{4.01g}{102.04g/mol}=0.039moles$

$C_9H_6O_3+C_4H_6O_3\rightarrow C_9H_8O_4+C_2H_3O_2$

According to stoichiometry :

1 mole of salycylic acid require 1 mole of acetic anhydride

Thus 0.023 moles of salycylic acid require= $\frac{1}{1}\times 0.023=0.023moles$ of acetic anhydride

Thus salycylic acid is the limiting reagent as it limits the formation of product and acetic anhydride is the excess reagent.

As 1 mole of salycylic give = 1 mole of aspirin

Thus 0.023 moles of salycylic acid give = $\frac{1}{1}\times 0.023=0.023moles$ of aspirin

Mass of aspirin = $moles\times {\text {Molar mass}}=0.023moles\times 180.15g/mol=4.14g$

Thus theoretical yield of aspirin is 4.14 g

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3 years ago

Which scientist arranged the elements in order of increasing atomic number, rather than increasing atomic mass?

pentagon [3]

Answer:

Henry Moseley

Explanation:

Dmitry Mendeleef and Lothar Meyer proposed a periodic table based on the atomic mass.

They stated a periodic law expressed as "chemical properties of elements are a periodic function of their atomic weights".

But, Henry Moseley in 1900s re-stated periodic law by changing the basis of the law from atomic weight to atomic number.

The present periodic law is stated as "the properties of elements are a periodic function of their atomic number".

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