Benedict's reagent (often called Benedict's qualitative solution or Benedict's solution) is a chemical reagent named after American chemist Stanley Rossiter Benedict.[1]
Benedict's test
Positive Benedict's test
ClassificationColorimetric methodAnalytesReducing sugars
It is a complex mixture of sodium carbonate, sodium citrate and copper(II) sulphate pentahydrate.[2] It is often used in place of Fehling's solution to detect the presence of reducing sugars. The presence of other reducing substances also gives a positive reaction.[3] Such tests that use this reagent are called the Benedict's tests. A positive test with Benedict's reagent is shown by a color change from clear blue to a brick-red precipitate.
Generally, Benedict's test detects the presence of aldehydes and alpha-hydroxy-ketones, also by hemiacetal, including those that occur in certain ketoses. Thus, although the ketose fructose is not strictly a reducing sugar, it is an alpha-hydroxy-ketone, and gives a positive test because it is converted to the aldoses glucose and mannose by the base in the reagent.
The principle of Benedict's test is that when reducing sugars are heated in the presence of an alkali they are converted to powerful reducing species known as enediols. Enediols reduce the cupric compounds (Cu2+) present in the Benedict's reagent to cuprous compounds (Cu+) which are precipitated as insoluble red copper(I) oxide(Cu2O).
The color of the obtained precipitate gives an idea about the quantity of sugar present in the solution, hence the test is semi-quantitative. A greenish precipitate indicates about 0.5 g% concentration; yellow precipitate indicates 1 g% concentration; orange indicates 1.5 g% and red indicates 2 g% or higher concentration.
Answer:
3.1 L
Explanation:
Step 1: Given data
- Mass of oxygen (m): 3.1 g
Step 2: Calculate the moles of oxygen
The molar mass of oxygen is 32.00 g/mol.
Step 3: Calculate the volume of the container
We will use the ideal gas equation.
P × V = n × R × T
V = n × R × T / P
V = 0.097 mol × (0.0821 atm.L/mol.K) × 390 K / 1.00 atm
V = 3.1 L
The change in pressure in a sealed 10.0L vessel is 5.28 atm
<u><em>calculation</em></u>
The pressure is calculated using the ideal gas equation
That is P=n RT
where;
P (pressure)= ?
v( volume) = 10.0 L
n( number of moles) which is calculated as below
<em>write the equation for decomposition of NH₄NO₂</em>
NH₄NO₂ → N₂ +2H₂O
<em>Find the moles of NH₄NO₂</em>
moles = molarity x volume in liters
= 2.40 l x 0.900 M =2.16 moles
<em>Use the mole ratio to determine the moles of N₂</em>
that is from equation above NH₄NO₂:N₂ is 1:1 therefore the moles of N₂ is also =2.16 moles
R(gas constant) =0.0821 l.atm/mol.K
T(temperature) = 25° c into kelvin = 25 +273 =298 K
make p the subject of the formula by diving both side by V
P = nRT/V
p ={ (2.16 moles x 0.0821 L.atm/mol.K x 298 K) /10.0 L} = 5.28 atm.
Answer:
The number of molecules in 5.83 moles of SO2 is 3.51*10^24 molecules
Explanation:
Step 1: Data given
Number of moles SO2 = 5.83 moles
Number of Avogadro = 6.022 * 10^23
Step 2: Calculate molecules SO2
Number of molecules = number of moles * number of Avogadro
Number of molecules = 5.83 * 6.022 *10^23 / moles
Number of molecules = 3.51*10^24 molecules
The number of molecules in 5.83 moles of SO2 is 3.51*10^24 molecules
Taking into account the definition of molarity, the concentration of the solution is 0.855 .
<h3>Definition of molarity</h3>
Molar concentration or molarity is a measure of the concentration of a solute in a solution and indicates the number of moles of solute that are dissolved in a given volume.
The molarity of a solution is calculated by dividing the moles of solute by the volume of the solution:
Molarity is expressed in units .
<h3>Molarity of NaCl</h3>
In this case, you have:
- number of moles of NaCl= 1.71 moles (being 58.45 g/mole the molar mass of NaCl)
- volume 2 L
Replacing in the definition of molarity:
Solving:
Molarity= 0.855
Finally, the concentration of the solution is 0.855 .
Learn more about molarity:
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