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aev [14]
2 years ago
14

when a candle burns both physical and chemical changes take place at identify these changes give another example of a familiar p

rocess in which both the chemical and physical changes takes place. ​
Chemistry
1 answer:
sp2606 [1]2 years ago
8 0

Answer:

So, the melting of wax and vapourisation of melted wax are physical changes. Chemical Changes : The wax near flame burns and gives new substances like carbon dioxide, carbon soot, water vapour, heat and light. LPG is another example of a familiar process in which both the chemical and physical changes take place.

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determine the ph of a buffer that is 0.55 M HNO2 and 0.75 M KNO2. tha value of Ka for HNO2 is 6.8*10^-4
Mariana [72]

Answer:

pH = 3.3

Explanation:

Buffer solutions minimize changes in pH when quantities of acid or base are added into the mix. The typical buffer composition is a weak electrolyte (wk acid or weak base) plus the salt of the weak electrolyte. On addition of acid or base to the buffer solution, the solution chemistry functions to remove the acid or base by reacting with the components of the buffer to shift the equilibrium of the weak electrolyte left or right to remove the excess hydronium ions or hydroxide ions is a way that results in very little change in pH of the system. One should note that buffer solutions do not prevent changes in pH but minimize changes in pH. If enough acid or base is added the buffer chemistry can be destroyed.

In this problem, the weak electrolyte is HNO₂(aq) and the salt is KNO₂(aq). In equation, the buffer solution is 0.55M HNO₂ ⇄ H⁺ + 0.75M KNO₂⁻ . The potassium ion is a spectator ion and does not enter into determination of the pH of the solution. The object is to determine the hydronium ion concentration (H⁺) and apply to the expression pH = -log[H⁺].

Solution using the I.C.E. table:

              HNO₂ ⇄    H⁺   +   KNO₂⁻

C(i)        0.55M       0M      0.75M

ΔC            -x            +x          +x

C(eq)  0.55M - x       x     0.75M + x    b/c [HNO₂] / Ka > 100, the x can be                                    

                                                             dropped giving ...

           ≅0.55M        x       ≅0.75M        

Ka = [H⁺][NO₂⁻]/[HNO₂] => [H⁺] = Ka · [HNO₂]/[NO₂⁻]

=> [H⁺] = 6.80x010⁻⁴(0.55) / (0.75) = 4.99 x 10⁻⁴M

pH = -log[H⁺] = -log(4.99 x 10⁻⁴) -(-3.3) = 3.3

Solution using the Henderson-Hasselbalch Equation:

pH = pKa + log[Base]/[Acid] = -log(Ka) + log[Base]/[Acid]

= -log(6.8 x 10⁻⁴) + log[(0.75M)/(0.55M)]

= -(-3.17) + 0.14 = 3.17 + 0.14 = 3.31 ≅ 3.3

3 0
3 years ago
In the chemical formula, is the metal or nonmetal symbol written first?
Nikitich [7]
<span>Chemical formulas are written from the most metllic 
for example group Alkali Metals are the most metallic, so they will be written first.</span>
6 0
3 years ago
Please help, and I’ll thank you.
coldgirl [10]

Answer:

There will be formed 13.82 grams of Fe3O4.

Explanation:

<u>Step 1:</u> the balanced reaction

3 Fe(s) + 4 H2O(l) —— Fe3O4(s) + 4 H2(g)

We see that for 3 moles Fe consumed, there will be consumed 4 moles of H20 and produced 1 mole of Fe3O4 and 4 moles of H2.

<u>Step 2:</u> Calculating moles

⇒mole = mass / Molar mass

⇒moles Fe = 10g / 55.845g/mole = 0.179 moles

⇒moles H2O = 10g / 18g/mole = 0.5556 moles

Since we have 4 moles of H2O consumed for 3 moles of Fe, this means that for 0.179 moles of Fe, we have :

0.179 / 4 *3 = 0.2387 moles of H2O consumed

This means that Fe will be completely consumed and there will remain 0.2387 moles of H2O.

Fe is the limiting reactant and H2O is in excess.

<u>Step 3: </u>Calculate moles of Fe3O4

For 3 moles of Fe consumed, we have 1 mole of Fe3O4 produced.

This means, that for 0.179 moles of Fe consumed, we have 0.179/3 =0.05967 molesof Fe3O4 produced.

<u>Step 4:</u> Calculating mass of Fe3O4

mass= number of moles * Molar mass

mass Fe3O4 = 0.05967 mole * 231.55g/mole = 13.8166 g ≈ 13.82grams of Fe3O4

There will be formed 13.82 grams of Fe3O4.

5 0
3 years ago
Identify whather the following are elements, compounds and mixture.
astra-53 [7]
1 is element 2 is element 3 is compound 4 is element 5 is nothing in and water is a compound
6 0
3 years ago
Which word equation shows hydrogen reacting with oxygen to form water?
Karo-lina-s [1.5K]
2H₂ + O₂ = 2H₂O
_______________________
3 0
3 years ago
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