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3 years ago

Does adding coefficients to a chemical equation disobey the law of definite proportions? Explain your answer.

Chemistry

1 answer:

Temka [501]3 years ago

3 0

Answer: No

Explanation:

- Law of definite proportions is a case from the Law of conservation of energy (matter) which states that "mass can neither be created nor destroyed, but changed from one form to another."

- Adding coefficients to a chemical equation confirms that there is the same number of atoms on both sides of a reaction; therefore, matter has not been created or destroyed but reorganized to give new substrates.

Example : 2 Mg + O2 → 2 MgO

In the balanced equation above, 2 moles of Mg reacts with 1 mole of O2 to produce 2 moles of MgO.

mass of 2 moles of Mg = 24×2= 48 grams

mass of 1 mole of O2 = 16+16 = 32 grams

total mass of reactants = 48 + 32 = 80 grams

mass of 2 moles of MgO = (24+16) ×2 = 80 grams

total mass of products = 80 grams

It is clear that the number of grams of matter before and after the reaction is the same and equals to 80 grams, so obeys the law of definite proportions..

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A beaker with 1.60×102 mL of an acetic acid buffer with a pH of 5.000 is sitting on a benchtop. The total molarity of acid and c

stich3 [128]

Answer:

The pH will change 0.16 ( from 5.00 to 4.84)

Explanation:

Step 1: Data given

volume of acetic acid buffer = 160 mL

The total molarity of acid and conjugate base in this buffer is 0.100 M

A student adds 7.10 mL of a 0.460 M HCl solution to the beaker.

The pKa of acetic acid is 4.740

pH = 5.00

Step 2: Calculate concentration of acid

Consider x = concentration acid

Consider y = concentration conjugate base

x + y = 0.100

5.00 = 4.740 + log y/x

5.00 - 4.740 = log y/x

0.26 = log y/x

10^0.26 =1.82 = y/x

1.82 x = y

Since x+y = 0.100

x + 1.82 x = 0.100

2.82 x = 0.100

x =0.0355 M = concentration acid

Step 3: Calculate concentration of conjugate base

y = 0.100 - x

0.100 - 0.0355 =0.0645 M= concentration conjugate base

Step 4: Calculate moles of acid

Moles = volume * molarity

moles acid = 0.160 L * 0.0355 M= 0.00568 moles

Step 5: Calculate moles of conjugate base

moles conjugate base = 0.0645 M * 0.160 L=0.01032 moles

Step 6: Calculate moles HCl

moles HCl = 7.10 * 10^-3 L * 0.460 M=0.003266 moles

Step 7: Calculate new moles

A- + H+ = HA

moles conjugate base = 0.01032 - 0.003266 =0.007054 moles

moles acid = 0.00568 + 0.003266=0.008946 moles

Step 8: Calculate the total volume

total volume = 160 + 7.10 = 167.1 mL = 0.1671 L

Step 9: Calculate the concentration of the acid

concentration acid = 0.008946/ 0.1671 =0.0535 M

Step 10: Calculate the concentration of conjugate base

concentration conjugate base = 0.007054/ 0.1671 =0.0422 M

Step 11: Calculate the pH

pH = 4.740 + log 0.0535/ 0.0422=4.84

change pH = 5.00 - 4.84=0.16

The pH will change 0.16

5 0

3 years ago

According to de Broglie, which of these objects does not have a wavelength?

polet [3.4K]

Answer: Option D is correct.

Explanation: Equation given by de Broglie is:

$\lambda =\frac{h}{mv}$

where, $\lambda$ = wavelength of the particle

h = Planck's constant

m = mass of the particle

v = velocity of the particle

In option A, football will have some mass and is moving with a velocity of 25 m/s, hence it will have some wavelength.

In Option B, unladen swallow also have some mass and is moving with a velocity of 38 km/hr, hence it will also have some wavelength.

In Option C, a person has some mass and is running with a velocity of 7 m/hr, hence it will also have some wavelength.

As, the momentum of these particles are large, therefore the wavelength will be of small magnitude and hence, is not observable.

From the above, it is clearly visible that all the options are having some wavelength, so option D is correct.

7 0

3 years ago

20 mL of 80°C water is mixed with 20 mL of 0°C water in a perfect calorimeter. What is the final temperature?

OLga [1]

Times it bye for then ur answer will be 80

5 0

2 years ago

Is 2 KNO₃ + H₂CO₃ → K₂CO₃ + 4 HNO₃ a balanced equation

krok68 [10]

Hey there!

The elements in this equation are K, N, O, H, and C.

Let's count how many of each are on each side to see if it is balanced.

K: 2 on the left, 2 on the right.

N: 2 on the left, 4 on the right.

O: 9 on the left, 6 on the right.

H: 2 on the left, 4 on the right.

C: 1 on the left, 1 on the right.

Notice that there are different amounts of N, O, and H on the left side and the right side.

This means that the equation is not balanced.

Hope this helps!

6 0

3 years ago

Matter is made up of heat energy and ___________energy?

ella [17]

You’re correct, matter is made up of heat energy and chemical energy

all matter contains heat because it is the result of the movement of atoms, molecules, or ions in solids, liquids, and gases.

all matter also contains chemical energy. chemical energy is stored in the bonds of chemical compounds so atoms and molecules are held together by chemical energy

hope this helps :)

3 0

2 years ago