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In-s [12.5K]
3 years ago
7

Which of the following statements holds true for a chemical change?

Chemistry
2 answers:
Anettt [7]3 years ago
8 0
C. in a chemical change the molecular structure changes.
ad-work [718]3 years ago
6 0

Answer : The correct option is C.

Explanation :

Chemical change : It is defined as a change in which a new compounds are formed by the chemical reaction. Changes occurs in their chemical composition and properties.

The molecular structure of a substance changes in a chemical reaction is a chemical change.

  • Change in molecular structure means that there is a breaking and formation of bonds in a molecule.

The example of chemical change in terms of change in molecular structure is the reaction of hydrogen with oxygen.

The reaction of hydrogen with oxygen is,

H_2(g)+O_2(g)\rightarrow 2H_2O(l)

In this reaction, the H-H bond is break and O-H bond is form.


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A sample of methane gas has a volume of 10 l at a pressure of 1.5 atm and a temperature of 20 °c. what volume does the gas occup
a_sh-v [17]
We can use combined gas laws to solve for the volume of the gas
 \frac{PV}{T}
where P - pressure, V - volume , T - temperature and k - constant
\frac{P1V1}{T1} = \frac{P2V2}{T2}
parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation 
T1 - temperature in Kelvin - 20 °C + 273 = 293 K
T2 - 40 °C + 273 = 313 K
substituting the values 
\frac{1.5 atm*10L}{293 K} =  \frac{0.9 atm*V}{313K}
V = 17.8 L
volume of the gas is 17.8 L 
7 0
3 years ago
Which pair of elements have the same valence electronic configuration of np³?
Dennis_Churaev [7]

Answer:

(c) P and Sb

Explanation:

We can determine the number of valence electrons of an element:

  • If it belongs to Groups 1 and 2, the number of valence electrons is equal to the number of group and the differential electron occupies the s subshell.
  • If it belongs to the groups 13-18, the number of valence electrons is equal to: "Number of group - 10" and the differential electron occupies the p subshell.

Which pair of elements have the same valence electronic configuration of np³?

(a) O and Se. NO. They belong to the group 16 and the valence electron configuration is ns² np⁴.

(b) Ge and Pb. NO. They belong to the group 14 and the valence electron configuration is ns² np².

(c) P and Sb. YES. They belong to the group 15 and the valence electron configuration is ns² np³.

(d) K and Mg. NO. They belong to the groups 1 and 2 and the valence electron configuration is ns¹ and ns².

(e) Al and Ga. NO. They belong to the group 13 and the valence electron configuration is ns² np¹.

5 0
3 years ago
Caffeine, a stimulant found in coffee and soda, has the following elemental composition: 49.48% carbon, 5.19% hydrogen, 16.48% o
prisoha [69]

Answer:

Explanation:

C = 49.48

H = 5.19

O = 16.48

N = 28.85

ratio of moles

= 49.48 / 12 : 5.19 / 1 : 16.48 / 16 : 28.85 / 14

= 4.123 : 5.19 : 1.03 : 2.06

= 4 : 5 : 1 : 2

so the empirical formula = C₄ H₅O N₂

Let molecular formula = (  C₄ H₅ON₂ )ₙ ,

n ( 48 + 5 + 16 + 28 ) = 119.19

97 n = 194.19

n = 2 ( approx )

molecular formula = C₈ H₁₀O₂ N₄

3 0
3 years ago
What are the trends and exceptions to the trends in electron affinity
slega [8]

Answer:

Explanation:

Electron affinity is the energy released in adding an electron to a neutral atom in the gas phase.

It is a measure of the readiness of an atom to gain an electron. This property is very peculiar to non-metals. The higher the value, the greater the tendency to accept electrons.

Across a period electron affinity increases due to the increasing nuclear charge not being compensated for.

Down a group, electron affinity decreases  due to the low nuclear charge and the large atomic radii.

The exception to this rule is the stability of half-filled sublevels. For example, nitrogen has a configuration of 2,5 with sublevel notation of 1s²2s²2p³.

The p-sublevel has a degeneracy of three and the three electrons goes in singly. This makes the configuration stable.

We expect such an atom to have a higher electron affinity but its configuration is stable and carbon would have a higher affinity than it across the same period.

Half filled sublevels are exception to the trend of electron affinity.

5 0
4 years ago
9) Which element in each pair has the larger ionization energy?
erastovalidia [21]
I think the answer is C.
6 0
3 years ago
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