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ladessa [460]
4 years ago
10

Both slicing a tomato and a chemical change such as burning toast cannot be reversed. However, why is slicing a tomato still con

sidered only a physical change?
Chemistry
2 answers:
iogann1982 [59]4 years ago
7 0

Physical changes do not change the chemical make up of a substance. Chemical changes do.

Slicing a tomato only changes its proportion and size (which are physical properties), instead of anything inside the tomato. while burning toast changes something inside the toast, making it a chemical change, instead of a physical change.

Molodets [167]4 years ago
3 0

Physical changes do not change the chemical make up of a substance. Chemical changes do.

Slicing a tomato only changes its proportion and size (which are physical properties), instead of anything inside the tomato.

Meanwhile, burning toast changes something inside the toast, making it a chemical change, instead of a physical change.

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How does the electron configuration of elements within the same group compare? (A.) They all have their valence electrons in the
lesya [120]

Answer:

B.They all have their valence electrons in the same type of subshell

Explanation:

  • The electron configurations of elements in the same group (column) of the periodic table have them in the same type of subshell.
  • But the subshells may be of different shells. Thus , the energies of them need not be the same.
  • For example , The Alkalai Metals are found in the first column of the periodic table Group IA. This set of elements all have valence electrons in only the 's' orbital and because they are in the first column they all have s^{1} configuration. i.e,
  1. H 1s^1
  2. Li 1s^2 2s^1
  3. Na 1s^2 2s^2 2p^6 3s^1
  4. K 1s^2 2s^2 2p^6 3s^2 3p^64s^1
5 0
3 years ago
Three chemistry students measured the length of a copper bar. The recorded lengths were 5.05 cm, 5 cm , and 5.1 cm, What is the
Salsk061 [2.6K]
5.05 + 5 + 5.1 = 15.15cm Then you just divide it by the amount of measurements you had like this:15.15 ÷ 3 = 5.04999971cm Then you can just round it to the 3rd figure: 5.05cm < And that's the mean/average length of the bar. :) (Or the one above if you want all of the decimals too) 
3 0
4 years ago
Suppose a student started with 142.0 mg of trans-cinnamic acid, 412 mg of pyridinium tribromide, and 2.30 mL of glacial acetic a
nirvana33 [79]

Answer: Theoretical Yield = 0.2952 g

               Percentage Yield = 75.3%

Explanation:

Calculation of limiting reactant:

n-trans-cinnamic acid moles = (142mg/1000) / 148.16 = 9.584*10⁻⁴ mol

pyridium tribromide moles = (412mg/1000) / 319.82= 1.288*10⁻³ mol

  • n-trans-cinnamic acid is the limiting reactant

The molar ratio according to the equation mentioned is equals to 1:1

The brominated product moles is also = 9.584*10⁻⁴ mol

Theoretical yield = (9.584*10⁻⁴ mol) * (Mr of brominated product)

                             =  (9.584*10⁻⁴ mol) * (307.97) = 0.2952 g

Percentage Yield is : Actual Yield / Theoretical Yield = 0.2223/0.2952

                                                                                           = 75.3%

4 0
4 years ago
What element has an atomic mass 4?
Daniel [21]

Answer:

Helium has atomic mass  4.002602.

So the answer to yr question is helium.

4 0
3 years ago
Read 2 more answers
A phosphate buffer is involved in the formation of urine. The developing urine contains H2PO4 and HPO42- in the same concentrati
Katen [24]

Answer:

The ionization equation is

H_{2}PO_{4}^{-}  +H_{2}O ⇄HPO_{4}^{-2}  +H_{3}O^{+} (1)

Explanation:

The ionization equation is

H_{2}PO_{4}^{-}  +H_{2}O ⇄HPO_{4}^{-2}  +H_{3}O^{+} (1)

As the Bronsted definition sais, an acid is a substance with the ability to give protons thus, H2PO4 is the acid and HPO42- is the conjugate base.

The Ka expression is the ratio between the concentration of products and reactants of the equilibrium reaction so,

Ka = \frac{[HPO_{4}^{-2}] [H_{3}O^{+}]}{[H_{2}PO_{4}^{-}] [H_{2}O]} = 6.2x10^{-8}

The pKa is

-Log (Ka) = -Log (6.2x10^{-8}) = 7.2

The pKa of H2CO3 is 6,35, thus this a stronger acid than H2PO4. The higher the pKa of an acid greater the capacity to donate protons.

In the body H2CO3 is a more optimal buffer for regulating pH due to the combination of the two acid-base equilibriums and the two pKa.

If the urine is acidified, according to Le Chatlier's Principle the equilibrium (1)  moves to the left neutralizing the excess proton concentration.

3 0
4 years ago
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