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azamat
3 years ago
5

Sharpening a pencil leaves behind pencil shavings. is sharpening a physical or chemical change

Chemistry
2 answers:
marta [7]3 years ago
7 0
Physical

because the pencil is not changing to a new substance, just changing form :)
IgorLugansk [536]3 years ago
6 0
Physical damage. 

If you burned the pencil, it would be considered chemical. 
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Which is a gas at room temperature?
dalvyx [7]

Answer:

Several of the nonmetals are gases in their elemental form. Elemental hydrogen (H, element 1), nitrogen (N, element 7), oxygen (O, element 8), fluorine (F, element 9), and chlorine (Cl, element 17) are all gases at room temperature, and are found as diatomic molecules (H2, N2, O2, F2, Cl2).

Explanation:

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3 years ago
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What is the organization that regulates the safety of Bluetooth and other wireless devices
Dimas [21]

Answer:

The U.S. Federal Communications Commission (FCC)

Explanation:

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3 years ago
Select the conjugate acid-base pair(s). a) HI, I b) HCHO2, SO4^2- c) CO3^2-, HCI d) PO4^3-, HPO4^2-
Semenov [28]

Answer:

d) PO4^3-, HPO4^2-

Explanation:

Basically, an acid and a base which differs only by the presence or absence of  proton (hydrogen ion) are called a conjugate acid-base pair.

a) HI, I

This is incorrect. For the acid, HI the conjugate base is I⁻ ion.

b) HCHO2, SO4^2-

This is incorrect, there's no relationship between both entities.

c) CO3^2-, HCI

This is incorrect, there's no relationship between both entities.

d) PO4^3-, HPO4^2-

This is correct. The difference between both entities is the Hydrogen ion. This is the conjugate acid-base pair

6 0
3 years ago
Gastric juice is made up of substances secreted from parietal cells, chief cells, and mucous-secreting cells. The cells secrete
neonofarm [45]

Answer:

The amount of energy required to transport hydrogen ions from a cell into the stomach is 37.26KJ/mol.

Explanation:

The free change for the process can be written in terms of its equilibrium constant as:

ΔG° = -RTInK_(eq)

where:

R= universal gas constant

T= temperature

K_eq= equilibrum constant for the process

Similarly, free energy change and cell potentia; are related to each other as follows;

ΔG= -nFE°

from above;

F = faraday's constant

n = number of electrons exchanged in the process; and  

E = standard cell potential

∴ The amount of energy required for transport of hydrogen ions from a cell into stomach lumen can be calculated as:

ΔG° = -RTInK_(eq)

where;

[texK_eq[/tex]=\frac{[H^+]_(cell)}{[H^+(stomach lumen)]}

For transport of ions to an internal pH of 7.4, the transport taking place can be given as:

H^+_{inside} ⇒ H^+_{outside}

Equilibrum constant for the transport is given as:

K_{eq}=\frac{[H^+]_{outside}}{[H^+]_{inside}}

=\frac{[H^+]_{cell}}{[H^+]_{stomach lumen}}

[H^+]_{cell}= 10⁻⁷⁴

=3.98 * 10⁻⁸M

[H^+]_{stomach lumen} = 10⁻²¹

=7.94 * 10⁻³M

Hence;

K_{eq}=\frac{[H^+]_{cell}}{[H^+]_{stomachlumen}}

=\frac{3.98*10^{-8}}{7.94*10{-3}}

= 5.012 × 10⁻⁶

Furthermore, free energy change for this reaction is related to the equilibrium concentration given as:

ΔG° = -RTInK_(eq)

If temperature T= 37° C ; in kelvin

=37° C + 273.15K

=310.15K; and

R-= 8.314 j/mol/k

substituting the values into the equation we have;

ΔG₁ = -(8.314J/mol/K)(310.15)TIn(5.0126*10^{-6})

= 31467.93Jmol⁻¹

≅ 31.47KJmol⁻¹

If the potential difference across the cell membrane= 60.0mV.

Energy required to cross the cell membrane will be:

ΔG₂ = -nFE°_{membrane}

ΔG₂ = -(1 mol)(96.5KJ/mol/V)(60*10^{-3})

= 5.79KJ

Therefore, for one mole of electron transfer across the membrane; the energy required is 5.79KJmol⁻¹

Now, we  can calculate the total amount of energyy required to transport H⁺ ions across the membrane:

Δ G_{total} = G_{1}+G_{2}

= (31.47+5.79) KJmol⁻¹

= 37.26KJmol⁻¹

We can therefore conclude that;

   The amount of energy required to transport ions from cell to stomach lumen is 37.26KJmol⁻¹

5 0
3 years ago
Write three sentences about The Amazing Life of Sand<br> HELP ASAP PLS
pishuonlain [190]

Answer:“If we’ve covered all of the potential sources, and we know the unique signature of the sand from these different sources, and we find it on a beach somewhere, then we basically know where it came from,” explained Barnard.

Explanation:

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3 years ago
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