Phenolphthalein Phenolphthalein is a universal indicator, which means it changes color to show the pH of certain solutions. Phenolphthalein stays colorless in acidic solutions and turns pink in alkaline solutions. Sodium hydroxide is a base, so when you add phenolphthalein, the solution turns pink. Other indicators commonly used in the laboratory are litmus and methyl orange. A Litmus indicator solution goes red in acidic solutions, blue in alkaline solutions and purple in neutral solutions. Methyl orange turns red in acidic solutions and yellow in neutral or alkaline solutions.
Answer:
C₄H₂N₂
Explanation:
First we<u> calculate the moles of the gas</u>, using PV=nRT:
P = 2670 torr ⇒ 2670/760 = 3.51 atm
V = 300 mL ⇒ 300/1000 = 0.3 L
T = 228 °C ⇒ 228 + 273.16 = 501.16 K
- 3.51 atm * 0.3 L = n * 0.082atm·L·mol⁻¹·K⁻¹ * 501.16 K
Now we<u> calculate the molar mass of the compound</u>:
- 2.00 g / 0.0256 mol = 78 g/mol
Finally we use the percentages given to<em> </em><u>calculate the empirical formula</u>:
- C ⇒ 78 g/mol * 61.5/100 ÷ 12g/mol = 4
- H ⇒ 78 g/mol * 2.56/100 ÷ 1g/mol = 2
- N ⇒ 78 g/mol * 35.9/100 ÷ 14g/mol = 2
So the empirical formula is C₄H₂N₂
The Reaction is spontaneous when temperature is 430 K. Hence, Option (C) is correct.
<h3>
</h3><h3>
What is Spontaneous reaction ?</h3>
Reactions are favorable when they result in a decrease in enthalpy and an increase in entropy of the system.
When both of these conditions are met, the reaction occurs naturally.
Spontaneous reaction is a reaction that favors the formation of products at the conditions under which the reaction is occurring.
According to Gibb's equation:
ΔG = ΔH - TΔS
ΔG = Gibbs free energy
ΔH = enthalpy change = +62.4 kJ/mol
ΔS = entropy change = +0.145 kJ/molK
T = temperature in Kelvin
- ΔG = +ve, reaction is non spontaneous
- ΔG = -ve, reaction is spontaneous
- ΔG = 0, reaction is in equilibrium
ΔH - TΔS = 0 for reaction to be spontaneous
T = ΔH / ΔS
Here,
T = 500K
Thus the Reaction is spontaneous when temperature is 500 K.
Learn more about Gibbs free energy here ;
https://brainly.in/question/13372282
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The second option only.
<h3>Explanation</h3>
A base neutralizes an acid when the two reacts to produce water and a salt.
Sulfuric acid H₂SO₄ is the acid here. There are more than one classes of bases that can neutralize H₂SO₄. Among the options, there are:
Metal hydroxides
Metal hydroxides react with sulfuric acid to produce water and the sulfate salt of the metal.
.
The formula for calcium sulfate 
in option A is spelled incorrectly. Why? The charge on each calcium 
is +2. The charge on each sulfate ion 
is -2. Unlike 
ions, it takes only one ion to balance the charge on each ion. As a result, and ions in calcium sulfate exist on a 1:1 ratio.
.
Ammonia, NH₃
Ammonia NH₃ can also act as a base and neutralize acids. NH₃ exists as NH₄OH in water:
.
The ion 
acts like a metal cation. Similarly to the metal hydroxides, NH₃ (or NH₄OH) neutralizes H₂SO₄ to produce water and a salt:
.
The formula of the salt (NH₄)₂SO₄ in the fourth option spelled the ammonium ion incorrectly.
As part of the salt (NH₄)₂SO₄, the ammonium ion NH₄⁺ is one of the products of this reaction and can't neutralize H₂SO₄ any further.
Answer:
violet
Explanation:
Waves with a short wavelength have the most energy. Red waves have a relatively long wavelength (in the 700 nm range), and violet waves are much shorter - roughly half that. Because violet waves have the shortest wavelength of the visible light spectrum, they carry the most energy (google)
