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Ksju [112]
4 years ago
14

The reaction nacl(s) → nacl(aq) is performed in a coffee cup calorimeter, using 100 ml of h2o(l) and 5.00g of nacl. if the tempe

rature of solution after mixing decreased by 2.30°c, what is the δhrxn in kj/mol? assume the heat capacities of all solutions are 4.18 j/g°c, and densities of all solutions are 1.00 g/ml. the molar mass of nacl is 58.44 g/mol
Chemistry
1 answer:
MrRissso [65]4 years ago
5 0

Since the density of water is 1 g /mL, hence there is 100 g of H2O. So total mass is:

m = 100 g + 5 g = 105 g

 

=> The heat of reaction can be calculated using the formula:

δhrxn = m C ΔT

where m is mass, C is heap capacity and ΔT is change in temperature = negative since there is a decrease

 

δhrxn = 105 g * 4.18 J/g°C * (-2.30°C)

δhrxn = -1,009.47 J

 

=> However this is still in units of J, so calculate the number of moles of NaCl.

 

moles NaCl = 5 g / (58.44 g / mol)

moles NaCl = 0.0856 mol

 

=> So the heat of reaction per mole is:

δhrxn = -1,009.47 J / 0.0856 mol

δhrxn = -11,798.69 J/mol = -11.8 kJ/mol

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How many molecules are in 6.0g of sodium phosphate?
Phantasy [73]

Answer:

2.2 x 10²² molecules.

Explanation:

  • Firstly, we need to calculate the no. of moles in (6.0 g) sodium phosphate:

<em>no. of moles = mass/molar mass </em>= (6.0 g)/(163.94 g/mol) = <em>0.0366 mol.</em>

  • <em>It is known that every mole of a molecule contains Avogadro's number (6.022 x 10²³) of molecules.</em>

<em />

<u><em>using cross multiplication:</em></u>

1.0 mole of sodium phosphate contains → 6.022 x 10²³ molecules.

0.0366 mole of sodium phosphate contains → ??? molecules.

<em>∴ The no. of molecules in  6.0 g of sodium phosphate</em> = (6.022 x 10²³ molecules)(0.0366 mole)/(1.0 mole) = <em>2.2 x 10²² molecules.</em>

3 0
3 years ago
How many of the following are oxidation-reduction reactions? I. reaction of a metal with a nonmetal II. synthesis III. combustio
nadezda [96]

Answer : The oxidation-reduction reactions are:

I. reaction of a metal with a nonmetal

II. synthesis

III. combustion

Explanation :

Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.

Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.

Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.

I. Reaction of a metal with a nonmetal :

When sodium react with chlorine gas then it react to give sodium chloride.

2Na+Cl_2\rightarrow 2NaCl

In this reaction, the oxidation state of sodium changes from (0) to (+1) and shows oxidation and the oxidation state of chlorine changes from (0) to (-1) and shows reduction. So, It is an oxidation-reduction reaction.

II. Synthesis reaction :

A chemical reaction where multiple substances or reactants combine to form a single product.

When hydrogen react with oxygen then it react to give water.

2H_2+O_2\rightarrow 2H_2O

In this reaction, the oxidation state of hydrogen changes from (0) to (+1) and shows oxidation and the oxidation state of oxygen changes from (0) to (-2) and shows reduction. So, It is an oxidation-reduction reaction.

III. Combustion reaction :

A chemical reaction in which a hydrocarbon reaction with the oxygen to give product as carbon dioxide and water.

When methane react with oxygen gas then it react to give carbon dioxide and water.

CH_4+2O_2\rightarrow CO_2+2H_2O

In this reaction, the carbon of methane gain oxygen and shows oxidation and the oxygen gas gain hydrogen and shows reduction. So, It is an oxidation-reduction reaction.

IV. Precipitation reaction :

It is defined as the reaction in which an insoluble salt formed when two aqueous solutions are combined.

The insoluble salt that settle down in the solution is known an precipitate.

It is a double displacement reaction. So, it is not an oxidation-reduction reaction.

V. Decomposition reaction :

A chemical reaction in which the the larger molecule decomposes to give two or more smaller molecules.

The oxidation state remains same on reactant and product side. So, it is not an oxidation-reduction reaction.

3 0
3 years ago
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The correct equation for the overall reaction can simply be obtained by adding the two separate equations together. Now when you add the two equations together, the overall K can be calculated by multiplying the individual K values. Therefore:<span>

K(overall) = K1 * K2 </span>

K(overall) = (1.6 x 10^-10) * (1.5 x 10^7)

<span>K(overall) = 2.4 x 10^-3</span>

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The correct answer would be B nuclear fission because an atom is splitting into two large fragments of comparable mass

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Answer:

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563,180 x -272.15 = -153,269,437 Celsius

I hope this helps :)

6 0
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