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dimulka [17.4K]
3 years ago
8

Calculate the number of milliliters of 0.753 M KOH required to precipitate all of the Pb2+ ions in 135 mL of 0.775 M Pb(NO3)2 so

lution as Pb(OH)2. The equation for the reaction is: Pb(NO3)2(aq) + 2 KOH(aq) Pb(OH)2(s) + 2 KNO3(aq) mL KOH
Chemistry
1 answer:
MrRa [10]3 years ago
3 0

Answer:

278 ml of KOH.

Explanation:

The equation for the reaction is: Pb(NO3)2(aq) + 2KOH(aq) --> Pb(OH)2(s) + 2KNO3(aq)

Pb(NO3)2:

Half ionic equation:

Pb(NO3)2(aq) --> Pb2+ + 2NO3^-

Pb(OH)2 --> Pb2+ + 2OH-

Volume = 135 mL

Molar concentration = 0.775 M

Number of moles = molar concentration * volume

= 0.775 * 0.135

= 0.105 mol of Pb(NO3)2

Since 1 mole of Pb(NO3)2 reacted with 2 moles of KOH to give 1 mole of Pb2+ (Pb(OH)2).

By stoichiometry,

Number of moles of KOH = 0.105 * 2

= 0.21 mol

Molar concentration = number of moles/volume

Volume = 0.21/0.753

= 0.278 l

To ml, 0.278 l * 1000 ml/1l

= 278 ml of KOH.

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If the pKa value for a given acid is low, what does that say about the acid (is it weak or strong)?
Dmitry [639]

Answer:

If the pKa of the acid is low (negative), then the acid is strong.

Explanation:

Ka, <em>the acid ionization constant,  </em>measures the strength of an acid in a solution. Stronger acids have higher Ka values.

We defined: pKa = -log[Ka]

This function is a decreasing function, meaning that pKa will be getting smaller and smaller,  while increasing Ka (high values of Ka will have negative pKa values). Therefore, stronger acids (high values of Ka), will have low (negative) pKa values.

3 0
3 years ago
What mass of carbon dioxide gas occupies a volume of 81.3L at 204 kPa and a temperature of 95.0°C?
alexandr1967 [171]

Answer:

236.9g

Explanation:

Given parameters:

Volume of gas  = 81.3L

Pressure of gas = 204kPa

temperature of gas = 95°C

Unknown:

Mass of carbondioxide gas = ?

Solution:

To solve this problem, the ideal gas law will be well suited. The ideal gas law is a fusion of Boyle's law, Charles's law and Avogadro's law.

Mathematically, it is expressed as;

                    PV = nRT

the unknown here is n which is the number of moles;

P is the pressure, V is the volume, R is the gas constant and T is the temperature.

convert pressure into atm

               101.325KPa  = 1atm

             204 kPa = \frac{204}{101.325}   = 2atm

Convert temperature to Kelvin;   95 + 273  = 368K

       2 x 81.3 = n x 0.082 x 368

             n = \frac{2 x 81.3}{0.082 x 368}   = 5.38moles

Since the unknown is mass;

 Mass  = number of moles x molar mass

      Molar mass of carbon dioxide  = 12 + 2(16)  = 44g/mol

 Mass  = 5.38 x 44  = 236.9g

5 0
3 years ago
A gold nugget has a density of 38.6g/cm3 and a mass of 270.2. what is its volume?​
aivan3 [116]

Density is given by the equation D=m/V, were D is density, m is mass in grams, and V is volume in cubic centimeters.


In this problem, we have density and we have mass so we can plug into the equation and solve for V.

38.6=270.2/V

<em>*Multiply both sides by V*</em>

38.6V=270.2

<em>*Divide both sides by 38.6*</em>

V=7


The volume of the gold nugget is 7cm3.


Hope this helps!!

5 0
3 years ago
Read 2 more answers
7.895 g + 3.4 g round to the correct number significant figures
DIA [1.3K]

Answer:

11.3 g

Explanation:

7.895 + 3.4 = 11.295

When rounded to correct number of significant figures --> 11.3

There are 3 significant figures in 11.3

7 0
3 years ago
Scientists can tell recycling reduces atmospheric emissions by knowing which of the following? o it takes more Btu to manufactur
Dmitriy789 [7]

Answer:

According to the Environmental Paper Network's Paper Calculator, it takes about 32 million BTUs of energy to produce 1 ton of virgin paper fiber. To produce 1 ton of recycled paper, it takes about 22 million BTUs.

so the answer could be it takes less Btu to manufacture recycled products than new ones

7 0
3 years ago
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