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galben [10]
3 years ago
13

Signs of a chemical change

Chemistry
2 answers:
dezoksy [38]3 years ago
5 0

Answer: There are five signs of chemical change

  • Color Change
  • Production of an odor
  • Change of Temperature
  • Evolution of Gas (bubbles start to form)
  • Precipitate (starts to form a solid)

When these signs start to form you know chemical change is at work.

Hope this helps :)

AnnZ [28]3 years ago
4 0
Some signs of a chemical change are a change in color and the formation of bubbles. The five conditions of chemical change: color chage, formation of a precipitate, formation of a gas, odor change, temperature change. Hope this helps!!
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compound 1 contains 15.0g of hydrogen and 120.0g oxygen. What is the percent compound of each element?
allsm [11]

Note down the formula below

\boxed{\sf Mass\%\;of\; element=\dfrac{Mass\:of\:the\: element}{Mass\;of\:the\: compound}\times 100}

Mass of the compound

\\ \sf\longmapsto 15+120=135g

Mass % of Hydrogen:-

\\ \sf\longmapsto \dfrac{15}{135}\times 100

\\ \sf\longmapsto \dfrac{1}{9}\times 100

\\ \sf\longmapsto 11.1\%

Mass % of Oxygen:-

\\ \sf\longmapsto \dfrac{120}{135}\times 100

\\ \sf\longmapsto \dfrac{8}{9}\times 100

\\ \sf\longmapsto 88.9\%

8 0
3 years ago
Is temperature beginning to rise a physical or chemical change?
Lelu [443]

Answer:

If temperature increases, as it does in most reactions, a chemical change is likely to be occurring. This is different from the physical temperature change. During a physical temperature change, one substance, such as water is being heated.

Explanation:

6 0
2 years ago
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The student wants to test the conductivity of each solution. Prior to carrying out the investigation, the student needs to ident
puteri [66]

Answer:b

Explanation: the particles will soon dissolve which means that the particles are changing but the volume is staying the same and the concentration is changing

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A buffer consists of 0.120 M HNO2 and 0.150 M NaNO2 at 25°C. pka of HNO2 is 3.40. a. What is the pH of the buffer? b. What is th
Mashcka [7]

Explanation:

It is known that K_{a} of HNO_{2} = 4.5 \times 10^{-4}.

(a)  Relation between K_{a} and pK_{a} is as follows.

                       pK_{a} = -log (K_{a})

Putting the values into the above formula as follows.

                      pK_{a} = -log (K_{a})

                                    = -log(4.5 \times 10^{-4})

                                     = 3.347

Also, relation between pH and  pK_{a} is as follows.

              pH = pK_{a} + log\frac{[conjugate base]}{[acid]}

                     = 3.347+ log \frac{0.15}{0.12}

                    = 3.44

Therefore, pH of the buffer is 3.44.

(b)   No. of moles of HCl added = Molarity \times volume

                                            = 11.6 M \times 0.001 L

                                             = 0.0116 mol

In the given reaction, NO^{-}_{2} will react with H^{+} to form HNO_{2}

Hence, before the reaction:

No. of moles of NO^{-}_{2} = 0.15 M \times 1.0 L

                                           = 0.15 mol

And, no. of moles of HNO_{2} = 0.12 M \times 1.0 L

                                               = 0.12 mol

On the other hand, after the reaction :  

No. of moles of NO^{-}_{2} = moles present initially - moles added

                                          = (0.15 - 0.0116) mol

                                          = 0.1384 mol

Moles of HNO_{2} = moles present initially + moles added

                               = (0.12 + 0.0116) mol

                                = 0.1316 mol

As, K_{a} = 4.5 \times 10^{-4}

           pK_{a} = -log (K_{a})

                         = -log(4.5 \times 10^{-4})

                         = 3.347

Since, volume is both in numerator and denominator, we can use mol instead of concentration.

As, pH = pK_{a} + log \frac{[conjugate base]}{[acid]}

            = 3.347+ log {0.1384/0.1316}

            = 3.369

            = 3.37 (approx)

Thus, we can conclude that pH after the addition of 1.00 mL of 11.6 M HCl to 1.00 L of the buffer solution is 3.37.

6 0
3 years ago
Solid diarsenic trioxide reacts with fluorine gas (F2) to produce liquid arsenic pentafluoride and oxygen gas (O2). Write the Qc
Flauer [41]

Answer:

QC= [O2]^3/[F2]^10

Explanation:

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