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3 years ago

How many H2O molecules are contained in 0.0016 moles of the hydrate Na2B4O7.10H2O?

2 answers:

8 0

Maybe this example could help you to understand this problem.

https://image.slidesharecdn.com/121howmanyatoms-091201144624-phpapp02/95/12-1-how-many-atoms-17-728....

MaRussiya [10]3 years ago

5 0

https://image.slidesharecdn.com/121howmanyatoms-091201144624-phpapp02/95/12-1-how-many-atoms-17-728....

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Jonas mixes citric acid with baking soda. How does he know the reaction is endothermic?

Kipish [7]

Answer:

D. The temperature of the the solution increases

Explanation:

Endothermic. Endo means in and thermic means a temperature, so Endothermic means the taking in of an temperature and the only answer choices that deal with temperature is,A and D. If it absorbs temperature it's going to rise.

6 0

3 years ago

Gaseous methane reacts with gaseous oxygen gas to produce gaseous carbon dioxide and gaseous water. If 2.59 g of water is produc

max2010maxim [7]

Answer: The percent yield of the water is 31.98 %

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

For methane:

Given mass of methane = 6.58 g

Molar mass of methane = 16 g/mol

Putting values in equation 1, we get:

$\text{Moles of methane}=\frac{6.58g}{16g/mol}=0.411mol$

For oxygen gas:

Given mass of oxygen gas = 14.4 g

Molar mass of oxygen gas = 32 g/mol

Putting values in equation 1, we get:

$\text{Moles of oxygen gas}=\frac{14.4g}{32g/mol}=0.45mol$

The chemical equation for the combustion of methane is:

$CH_4+2O_2\rightarrow CO_2+2H_2O$

By Stoichiometry of the reaction:

2 moles of oxygen gas reacts with 1 mole of methane

So, 0.45 moles of oxygen gas will react with = $\frac{1}{2}\times 0.45=0.225mol$ of methane

As, given amount of methane is more than the required amount. So, it is considered as an excess reagent.

Thus, oxygen gas is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction

2 moles of oxygen gas produces 2 moles of water

So, 0.45 moles of oxygen gas will produce = $\frac{2}{2}\times 0.45=0.45$ moles of water

Now, calculating the mass of water from equation 1, we get:

Molar mass of water = 18 g/mol

Moles of water = 0.45 moles

Putting values in equation 1, we get:

$0.45mol=\frac{\text{Mass of water}}{18g/mol}\\\\\text{Mass of water}=(0.45mol\times 18g/mol)=8.1g$

To calculate the percentage yield of water, we use the equation:

$\%\text{ yield}=\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100$

Experimental yield of water = 2.59 g

Theoretical yield of water = 8.1 g

Putting values in above equation, we get:

$\%\text{ yield of water}=\frac{2.59g}{8.1g}\times 100\\\\\% \text{yield of water}=31.98\%$

Hence, the percent yield of the water is 31.98 %

4 0

3 years ago

Calculate the volume of a sample of iron that has a density of 6.8 g/mL and a mass of 6780 mg.

Veronika [31]

Answer:

m= 6780mg = 6.78g = 6.8g

d= 6.8g/ml

V= m/d

V= 1ml

8 0

3 years ago

How does heat differ from temperature?

mote1985 [20]

Answer: Option (c) is the correct answer.

Explanation:

Temperature is used as for measuring the average kinetic energy present in a substance or object.

The internal kinetic energy obtained by the molecules of an object is known as thermal energy.

Hence, temperature measures the thermal energy of an object.

Whereas when this thermal energy flows from a hotter object to a cooler object which are placed adjacent to each other then it is known that heat is flowing.

Thus, we can conclude that heat differ from temperature as temperature measures thermal energy, and heat is the flow of thermal energy.

7 0

3 years ago

Read 2 more answers

Rank the following atoms in order of decreasing first ionization energies (i.e., highest to lowest): Li, Be, Ba, F.

Minchanka [31]

Answer:

The order is:

F >Be >Li >Ba

Explanation:

Electrons are held in atoms by their attraction to the nucleus which means that to remove an electron from the atom energy is needed.

The ionization energy is the minimum energy necessary to remove an electron from an atom in the gas phase and ground state, the electron removed being the outermost, that is, the furthest from the nucleus. The further away the electron is from the nucleus, the easier it is to remove it, that is, the less energy is needed.

By increasing the atomic number of the elements of the same group, the nuclear attraction on the outermost electron decreases, since the atomic radius increases. Then the ionization energy decreases. In other words, in a group it decreases from top to bottom because the size of the atom increases and it is easier to remove an external electron.

By increasing the atomic number of the elements of the same period, the nuclear attraction on the outermost electron increases, since the atomic radius decreases. Therefore, in a period, as the atomic number increases, the ionization energy increases. In summary, in a period it increases from left to right as the effective nuclear charge increases and it increases thanks to the decrease in the size of the atom.

Taking these considerations into account, the order is:

F >Be >Li >Ba

5 0

3 years ago