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Alexeev081 [22]

3 years ago

7

One isotope of oxygen has 8 protons and 10 neutrons. Which is the correct reference for this isotope? A. oxygen-18 B. oxygen-2 C

. oxygen-8 D. oxygen-10

1 answer:

hammer [34]3 years ago

5 0

A. Oxygen-18 is the correct reference for this isotope. As this notation requires the name of the element followed by a dash and the mass number of that corresponding element. The mass number is obtained by adding the number of protons and neutrons together as in this example.

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You place 36.5 ml of 0.266 M Ba(OH)2 in a coffee-cup calorimeter at 25.00°C and add 56.6 ml of 0.648 M HCl, also at 25.00°C. Aft

olya-2409 [2.1K]

Answer : The enthalpy of reaction $(\Delta H_{rxn})$ is, -96.9 kJ/mole

Explanation :

First we have to calculate the mass of solution.

$Mass=Density\times Volume$

Volume of solution = Volume of HCl + Volume of $Ba(OH)_2$

Volume of solution = 56.6 mL + 36.5 mL

Volume of solution = 93.1 mL

Density of solution = 1 g/mL

$Mass=1g/mL\times 93.1mL=93.1g$

The mass of solution is, 93.1 grams.

Now we have to calculate the heat released in the system.

Formula used :

$Q=m\times c\times \Delta T$

or,

$Q=m\times c\times (T_2-T_1)$

where,

Q = heat released = ?

m = mass = 93.1 g

$C_p$ = specific heat capacity of water = $4.184J/g^oC$

$T_1$ = initial temperature = $25.0^oC$

$T_2$ = final temperature = $29.83^oC$

Now put all the given value in the above formula, we get:

$Q=93.1g\times 4.184J/g^oC\times (29.83-25.00)^ioC$

$Q=1881.43J=1.88kJ$ (1 kJ = 1000 J)

Now we have to calculate the moles of $Ba(OH)_2$ and HCl.

$\text{Moles of }Ba(OH)_2=\text{Concentration of }Ba(OH)_2\times \text{Volume of solution}$

$\text{Moles of }Ba(OH)_2=0.266M\times 0.0365L=9.71\times 10^{-3}mol$

and,

$\text{Moles of }HCl=\text{Concentration of }HCl\times \text{Volume of solution}$

$\text{Moles of }HCl=0.648M\times 0.0566L=3.66\times 10^{-2}mol$

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

$Ba(OH)_2+2HCl\rightarrow BaCl_2+2H_2O$

From the balanced reaction we conclude that

As, 1 mole of $Ba(OH)_2$ react with 2 mole of $HCl$

So, $9.71\times 10^{-3}$ moles of $Ba(OH)_2$ react with $9.71\times 10^{-3}\times 2=0.0194$ moles of $HCl$

From this we conclude that, $HCl$ is an excess reagent because the given moles are greater than the required moles and $Ba(OH)_2$ is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of $H_2O$

From the reaction, we conclude that

As, 1 mole of $Ba(OH)_2$ react to give 2 mole of $H_2O$

So, $9.71\times 10^{-3}$ moles of $Ba(OH)_2$ react with $9.71\times 10^{-3}\times 2=0.0194$ moles of $H_2O$

Now we have to calculate the change in enthalpy of the reaction.

$\Delta H_{rxn}=-\frac{q}{n}$

where,

$\Delta H_{rxn}$ = enthalpy of reaction = ?

q = heat of reaction = 1.88 kJ

n = moles of reaction = 0.0194 mole

Now put all the given values in above expression, we get:

$\Delta H_{rxn}=-\frac{1.88kJ}{0.0194mole}=-96.9kJ/mole$

The negative sign indicates that the heat is released.

Therefore, the enthalpy of reaction $(\Delta H_{rxn})$ is, -96.9 kJ/mole

3 0

4 years ago

True or False;<br> aa is faster moving lava than pahoehoe?

frosja888 [35]

Answer:

It is false :l

Explanation:

Pahoehoe is a smooth and continuous lava crust. Pahoehoe forms when the effusion rate is low and consequently the velocity of lava flow is slow. Pahoehoe lava flow is usually at least 10 times slower than typical aa lava flow.

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7 0

3 years ago

Which of the following is NOT a characteristic of stars? A) Size B) temperature C) texture D) color

Lynna [10]

Answer:

C

Explanation:

Characteristics used to classify stars include color, temperature, size, composition, and brightness.

7 0

3 years ago

Let’s say that you have a solvatochromic compound that appears red in a solvent. You dissolve the compound in another solvent an

EastWind [94]

Answer:

Hypsochromic compound, More polar solvent

Explanation:

Hypsochromic shift refers to the shift of solution colour to blue side of the visible spectrum (blueshift) with increasing polarity of the solvent. In our case, the solution changes to orange colour from red when solvent is changed. This means that the emission spectrum of the solution underwent blueshift. (As orange colour is on the 'blue' side for red colour.) So this is a hypsochromic shift, and the new solvent is more polar that the previous one, as it caused hypsochromic shift.

7 0

3 years ago

Which of these takes place when a chemical change occurs? option 1: Bonds connecting atoms in products and reactants form. optio

Tamiku [17]

Answer: Out of the given options bonds connecting atoms in reactants break, and bonds connecting atoms in products form are the changes which takes place when a chemical change occurs.

Explanation:

A change that leads to the change in chemical composition of a substance is called a chemical change.

For example, $2NH_{3} \rightarrow N_{2} + 3H_{2}$

Here, bond between the reactant atoms nitrogen and hydrogen is broken down.

On the other hand, bond connecting the products that is $N_{2}$ and $H_{2}$ is formed.

Thus,, we can conclude that out of the given options bonds connecting atoms in reactants break, and bonds connecting atoms in products form are the changes which takes place when a chemical change occurs.

4 0

3 years ago