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lions [1.4K]
3 years ago
11

The forensic technician at a crime scene has just prepared a luminol stock solution by adding 13.0 g of luminol into a total vol

ume of 75.0 mL of H2O. What is the molarity of the stock solution of luminol?
Chemistry
1 answer:
Andrews [41]3 years ago
3 0

Answer:

0.978 M

Explanation:

Given data

  • Mass of luminol (solute): 13.0 g
  • Volume of the solution = volume of water: 75.0 mL = 0.0750 L

We can find the molarity of the stock solution of luminol using the following expression.

M = mass of solute / molar mass of solute × liters of solution

M = 13.0 g / 177.16 g/mol × 0.0750 L

M = 0.978 M

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How much heat is required to convert 20.0 g of ice at 50.0⁰C to liquid water at 0.0⁰C? The specific heat of ice is 2.06 J/(g∙⁰C)
Alex777 [14]

Answer:

8740 joules are required to convert 20 grams of ice to liquid water.

Explanation:

The amount of heat required (Q), measured in joules, to convert ice at -50.0 ºC to liquid water at 0.0 ºC is the sum of sensible heat associated with ice and latent heat of fussion. That is:

Q = m\cdot [c\cdot (T_{f}-T_{o})+L_{f}] (1)

Where:

m - Mass, measured in grams.

c - Specific heat of ice, measured in joules per gram-degree Celsius.

T_{o}, T_{f} - Temperature, measured in degrees Celsius.

L_{f} - Latent heat of fussion, measured in joules per gram.

If we know that m = 20\,g, c = 2.06\,\frac{J}{g\cdot ^{\circ}C}, T_{f} = 0\,^{\circ}C, T_{o} = -50\,^{\circ}C and L_{f} = 334\,\frac{J}{g }, then the amount of heat is:

Q = (20\,g)\cdot \left\{\left(2.06\,\frac{J}{g\cdot ^{\circ}C} \right)\cdot [0\,^{\circ}C-(-50\,^{\circ}C)]+334\,\frac{J}{g} \right\}

Q = 8740\,J

8740 joules are required to convert 20 grams of ice to liquid water.

3 0
2 years ago
How many grams are in 4 moles of Calcium?
mixer [17]

Answer:

160.32 grams of Ca or 160 if rounded

Explanation:

Multiply moles of Ca by the conversion factor (molar mass of calcium) 40.08 g Ca/ 1 mol Ca, which then allows the cancelation of moles, leaving grams of Ca.

4 mol*40.08g/mol = 160.32 grams of Ca

please give thanks by clicking heart button :)

3 0
2 years ago
Read 2 more answers
Select the substance that is thought to be partially responsible for depleting the concentration of ozone in the stratosphere. s
gogolik [260]

Answer:

cfcl3

Explanation:

When the cfcl3 in the atmosphere is hit by UV rays from the sun, it decomposes to Cl atoms. These Cl atoms then react with the ozone producing O2 and ClO. The ClO bombard with O atoms splitting the ClO up and the free Cl atom again bonds to another O3 molecule hence reducing it. One ClO can reduce several O3 molecules (up to 100,000) creating an ozone hole.

2Cl + O3 → 2ClO + 2O2

2ClO + 2O → 2Cl + 2O2

6 0
3 years ago
If 0.060 faraday is passed through an electrolytic cell containing a solution of In3+ ions, the maximum number of moles of In th
stira [4]

Answer: option B. 0.020 mole

Explanation:Please see attachment for explanation

8 0
3 years ago
The Michaelis-Menten equation is an expression of the relationship between the initial velocity,V0, of an enzymatic reaction and
antiseptic1488 [7]

Answer:

Option 2, Half of the active sites are occupied by substrate

Explanation:

Michaelis-Menten expression for enzyme catalysed equation is as follows:

V_0=\frac{V_{max\ [S]}}{k_M+[S]}

Here, K_m is Michaelis-Menten constant and [S] is substrate concentration.

When [S]=Km

Rearrange the above equation as follows:

V_0=\frac{V_{max}[S]}{k_M+[S]}\\V_0=\frac{V_{max}[S]}{[S]+[S]}\\V_0=\frac{V_{max}[S]}{2[S\\]}\\V_0=\frac{V_{max}}{2}

when [S]=Km, the rate of enzyme catalysed reaction becomes half of the maximum rate, that means half of the active sites are occupied by substrate.

Therefore, the correct option is option 2.

4 0
3 years ago
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