7th grade science help me plsssss

Answer: The value of [tex]\Delta H[/tex] is -163 kJZ

Explanation:

The number of moles is defined as the ratio of the mass of a substance to its molar mass. The equation used is:

[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex] ......(1)

We are given:

Given mass of water = 72.0 g

Molar mass of water = 18 g/mol

Putting values in equation 1, we get:

[tex]\text{Moles of water}=\frac{72.0g}{18g/mol}\\\\\text{Moles of water}=4mol[/tex]

Calculating the heat released for the condensation process:

[tex]\Delta H=n\times \Delta H_{(vap)}[/tex] ......(2)

where,

[tex]\Delta H[/tex] = amount of heat released

n = number of moles of water = 4 moles

[tex]\Delta H_{(vap)}[/tex] = specific heat of vaporization = -40.7 kJ/mol

Negative sign represents the amount of heat released.

Putting values in equation 2:

[tex]\Delta H=4mol\times (-40.7kJ/mol)=-163kJ[/tex]

Hence, the value of [tex]\Delta H[/tex] is -163 kJ

Answer:

D. Point into Leaf: water(H₂O), carbon dioxide (CO₂) sunlight, Point away from leaf: Sugars, oxygen (O₂)

Explanation:

Photosynthesis is the process used in the production of chemical energy in the form of energy containing organic compounds and oxygen from atmospheric carbon dioxide and liquid water enabled with the energy captured from light (mainly Sunlight) by the chlorophyll in green plants and other organisms

The basic chemical reaction involved in a photosynthesis reaction is presented as follows;

[tex]{}[/tex]                                    Sunlight

[tex]{}[/tex]                                          ↓

[tex]{}[/tex]       CO₂           +  H₂O (l)  →   C₆H₁₂O₆   +    O₂

Carbon dioxide [tex]{}[/tex]  Water        Glucose       Oxygen    

Answer: The correct net ionic equation for the reaction is [tex]2H^{+}(aq)+2OH^{-}(aq)\rightarrow 2H_2O(l)[/tex]

Explanation:

Net ionic equation is defined as the equations in which spectator ions are not included.

Spectator ions are the ones that are present equally on the reactant and product sides. They do not participate in the reaction.  

The balanced molecular equation is:

[tex]Ca(OH)_2(aq)+H_2SO_4(aq)\rightarrow CaSO_4(aq)+2H_2O(l)[/tex]

The complete ionic equation follows:

[tex]Ca^{2+}(aq)+2OH^-(aq)+2H^+(aq)+SO_4^{2-}(aq)\rightarrow 2Ca^{2+}(aq)+SO_4^{2-}(aq)+H_2O(l)[/tex]

As calcium and sulfate ions are present on both sides of the reaction. Thus, they are considered spectator ions.

The net ionic equation follows:

[tex]2H^{+}(aq)+2OH^{-}(aq)\rightarrow 2H_2O(l)[/tex]

Hence, the correct net ionic equation for the reaction is [tex]2H^{+}(aq)+2OH^{-}(aq)\rightarrow 2H_2O(l)[/tex]

Answer:

B. no reaction     

Explanation:

Hola aquí va la respuesta!

Se fomentó la inmigración europea porque la economía no era buena y vinieron a Paraguay para mejorar su situación.

Hola aquí va la respuesta!

Se fomentó la inmigración europea porque la economía no era buena y vinieron a Paraguay para mejorar su situación.

Answer:

Please find the answer to the question below

Explanation:

In chemistry, the following mathematical formula is used to calculate the number of moles contained by a substance:

mole = mass of substance (g)/molar mass of substance (g/mol)

Molar mass of salicylic acid (C7H6O3) = 12(7) + 1(6) + 16(3)

= 84 + 6 + 48

= 138g/mol

Mass = 5.50grams

mole = 5.5/138

mole = 0.039

Approximately, the number of moles of 5.5grams of salicylic acid is 0.04moles. This is in accordance with the mole value (0.04) given in this question.

Answer:

Just add a plenty of dots in the first one and very few dots in the second one

An area with high population density will have many dots while areas will low population density will have few dots when using dots to illustrate population density.

Population density is the ratio of the total number of organisms found in a given area to the total of the area of that place or habitat.

An area with high population density indicates that more organised ate found per unit area than an area with low population density.

Therefore, using dots to illustrate population density, an area with high population density will have plenty dots while areas will low population density will have few dots scattered over.

Learn more about population density at: https://brainly.com/question/13902749

Answer:

That is, a pH meter is useful in detecting or knowing the acidity (due to ions) or alkalinity (due to ions) of a solution. Thus, we can conclude that out of the given options it is true about a pH meter that it can be used in any acid-base titration

Answer: D. It can be used in any acid-base titration.

Explanation:

Answer:

B. Prepare solutions of different acid concentrations, measure 50 milliliters of each into different beakers, and place metal samples of different types but of the same mass into the beakers.

Explanation:

Since Michael is studying the factors that affect corrosion of metals, and wants to test the effect that different concentrations of an acid will have on the corrosion of a metal, using different acid concentrations of the same volume on different metal samples of the same size would give a much better than all the other options because, a standard volume of acid is used and also a standard mass of metal is used. So, the effect can be measured quantitatively since we have the same quantity of sample.

So, option B is the answer