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givi [52]
3 years ago
15

Which of the following is an example of a chernical change?

Chemistry
2 answers:
matrenka [14]3 years ago
7 0

Answer:

the chemical change occur in burning paper.

boiling water does not make any chemical change

melting gold "

dissolving sugar in water "

in these examples the reactant remains as the same , even if you melt gold it is gold itself, it only change its state.

AVprozaik [17]3 years ago
6 0
Answer:

Burning paper.

Explanation:

A chemical change is a change that changes the molecular structure of the substance you are changes. Boiling water would make water vapour, which is still water thus it is a physical change. Dissolving sugar in water is still sugar in water thus it is a physical change. Melting gold makes liquid gold which is still gold thus it is a physical change. Burning paper however changes from paper to ash and smoke, which are different on the molecular level, therefore it is a chemical change.
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No' of molecules divide by avogadro number , 6×6.023×10^23 so (2.2×10^22)÷(6.023×10^23)
= 0.03653 moles
moles × Molar mass = mass
n×Mr=m
0.03653×40 = 1.46 grams
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3 years ago
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(Please Help!) Aluminum reacts with oxygen to produce aluminum oxide (AI203). The balanced chemical equation for this reaction i
andriy [413]

#1

Moles of Oxygen =3

Molecules:-

  • 3×Avagadro no
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  • 18.066×10²³
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#2

Its because according to law of conservation of mass- Mass is neither created nor destroyed

AS ITS BALANCED SO BOTH SIDES ARE SAME .

HENCE THEY OBEY

5 0
2 years ago
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Write a balanced chemical equation for the standard formation reaction of solid sodium hydrogen carbonate nahco3 .
NNADVOKAT [17]
There are a number of methods of which we can form sodium bicarbonate. This compound is commonly known as baking soda. It can be prepared from the reaction of sodium hydroxide and carbonic acid. Carbonic acid in water dissociates into hydrogen ions and the bicarbonate ion while sodium hydroxide would ionize into sodium ions and hydroxide ions. With this, these ions would react and form the sodium bicarbonate salt and water. The chemical reaction would be expressed as follows:

NaOH + H2CO3 = H2O + NaHCO3

Sodium bicarbonate is used in cooking, as a toothpaste and as a cleaning substance.  Also, it is used in medical applications like for the preparation of the dialysate solution.
5 0
3 years ago
Calculate the ph of a 0.20 m solution of iodic acid (hio3, ka = 0.17).
saveliy_v [14]
Iodic acid partially dissociates into H+ and IO3- 
Assuming that x is the concentration of H+ at equilibrium, and sine the equation says the same amount of IO3- will  be released as that of H+, its concentration is also X.  The formation of H+ and IO3- results from the loss of HIO3 so its concentration at equilibrium is 0.20 M - x
Ka = [H+] [IO3-] / [HIO3]; 
<span>Initially, [H+] ≈ [IO3-] = 0 and [HIO3] = 0.20; </span>
<span>At equilibrium [H+] ≈ [IO3-] = x and [HIO3] = 0.20 - x; </span>
<span>so 0.17 = x² / (0.20 - x); </span>
<span>Solving for x using the quadratic formula: </span>
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7 0
3 years ago
50.0 ml of 0.010m naoh was titrated with 0.50m hcl using a dropper pipet. if the average drop from the pipet has a volume of 0.0
creativ13 [48]

25 drops of acid is required to neutralize the 50.0 ml of 0.010m of NaOH in the experiment.

The equation of the reaction is;

NaOH(aq) + HCl(aq) ---------> NaCl(aq) + H2O(l)

We can use the titration formula;

CAVA/CBVB = NA/NB

CA= concentration of acid

VA = volume of acid

CB = concentration of base

VB = volume of base

NA = number of moles of acid

NB = number of moles of base

CB = 0.010 M

VB = 50.0 ml

CA = 0.50 M

VA = ?

NA = 1

NB = 1

Substituting values;

CAVANB = CBVBNA

VA =  0.010 ×  50.0 × 1/ 0.50 × 1

VA = 1 ml

Since the total volume of acid used is 1 ml and each drop contains 0.040 ml

The number of drops required is 1ml/0.040 ml = 25 drops

Learn more: brainly.com/question/1527403

4 0
3 years ago
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