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3 years ago

All elements are pure substances. True False

1 answer:

5 0

It can be a compound or a single element. An element is a pure substance that cannot be separated into simpler substances by chemical or physical means. There are about 117 elements, but carbon, hydrogen, nitrogen and oxygen are only a few that make up the largest portion of Earth.
hopefully that helps

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A meal containing a burger, fries, and a milkshake contains 53.0 grams of fat, 38.0 grams of protein, and 152 grams of carbohydr

RSB [31]

Answer:

286 minutes

Explanation:

Given the content of fat in a meal= 53g

the content of protien in a meal= 38g

the content of carbohydrate in a meal= 152g

Also given that fuel value of protien = 17 KJ/g

the fuel value of fat = 38 KJ/g

the fuel value of carbohydrate = 17 KJ/g

Now to burn all the molecules the energy recquired is content of molecule times the fuel value.

the energy recquired to burn fat = $53\times 38=2014KJ$

the energy recquired to burn protien = $38\times 17=646KJ$

the energy recquired to burn carbohydrate = $152 \times 17=2584KJ$

The total energy=2014+646+2584=5244KJ

The energy spent on swimming is 1100KJ/hour

for 1 hour 1100 KJ are spent

to spend 5244 KJ of energy the time taken is = $\frac{5244}{1100}$ =4.76hours

We know 1 hour=60 minutes

The total time = $4.76\times 60=286minutes$

6 0

3 years ago

A chemist titrates of a hypochlorous acid solution with solution at . Calculate the pH at equivalence. The of hypochlorous acid

const2013 [10]

The question is incomplete, here is the complete question:

A chemist titrates 110.0 mL of a 0.2412 M hypochlorous acid (HCIO) solution with 0.0613 M NaOH solution at 25°C. Calculate the pH at equivalence. The pKa of hypochlorous acid is 7.50. Round your answer to 2 decimal places

Answer: The pH of the solution is 10.09

Explanation:

To calculate the volume of base, we use the equation given by neutralization reaction:

$n_1M_1V_1=n_2M_2V_2$

where,

$n_1,M_1\text{ and }V_1$ are the n-factor, molarity and volume of acid which is $HClO$

$n_2,M_2\text{ and }V_2$ are the n-factor, molarity and volume of base which is NaOH.

We are given:

$n_1=1\\M_1=0.2412M\\V_1=110.0mL\\n_2=1\\M_2=0.0613M\\V_2=?mL$

Putting values in above equation, we get:

$1\times 0.2412\times 110.0=1\times 0.0613\times V_2\\\\V_2=\frac{1\times 0.2412\times 110.0}{1\times 0.0613}=432.8mL$

At equivalence, the number of moles of acid is equal to the number of moles of base. Also, the moles of salt which is NaClO will also be the same.

To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in mL)}}$ .....(1)

For HClO:

Molarity of HClO solution = 0.2412 M

Volume of solution = 110.0 mL

Putting values in equation 1, we get:

$0.2412M=\frac{\text{Moles of HClO}\times 1000}{110}\\\\\text{Moles of HClO}=\frac{(0.2412\times 110)}{1000}=0.026532mol$

For NaClO:

Moles of NaClO = 0.026532 moles

Volume of solution = [432.8 + 110] mL = 542.8 mL

Putting values in above equation, we get:

$\text{Molarity of NaClO}=\frac{0.026532\times 1000}{542.8}=0.0489M$

To calculate the pH of the solution, we use the equation:

$pH=7+\frac{1}{2}[pK_a+\log C]$

where,

$pK_a$ = negative logarithm of weak acid which is hypochlorous acid = 7.50

C = concentration of the salt = 0.0489 M

Putting values in above equation, we get:

$pH=7+\frac{1}{2}[7.50+\log (0.0489)]\\\\pH=7+3.09=10.09$

Hence, the pH of the solution is 10.09

4 0

3 years ago

Assuming you have 6.24 x 1014 electrons and the surface area of the pail is 0.2 m2, what is the charge density (C/m2)?

pentagon [3]

Answer:

σ = 4.998 E-4 C/m²

Explanation:

1 Coulomb (C) ≡ 6.241509 E18 electrons (e)

∴ # elect = 6.24 E14 elect

charge (Q):

⇒ Q = (6.24 E14 elect)/( 1 C /6.241509 E18 elect) = 9.998 E-5 C

charge density (σ):

σ = Q/S

∴ surface area (S) = 0.2 m²

⇒ σ = ( 9.998 E-5 C ) / ( 0.2 m²)

⇒ σ = 4.998 E-4 C/m²

4 0

3 years ago

The smallest unit which maintains the physical properties of a compound is a(n _____. atom element molecule alloythe smallest un

LuckyWell [14K]

The answer that would best complete the given statement above is the term ATOM. The smallest unit which maintains the physical properties of a compound is an ATOM. But for a compound, it would be molecule. Hope this answers your question.

5 0

4 years ago

Check out the PNG below! Thank you to the person out there!

Lady bird [3.3K]

Answer:

4 Ethanol has a boiling point of 89 C at standard pressure.

6 0

4 years ago