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Alex787 [66]
3 years ago
6

How many grams of kbr must be dissolved to make 25.0 ml of a solution that has a molarity of 0.85 m?

Chemistry
1 answer:
lyudmila [28]3 years ago
4 0
Molarity is defined as the number of moles of solute in 1 L of solution 
molarity of solution to be prepared is 0.85 M
this means that there should be 0.85 mol of KBr in 1 L of solution 
if 1 L contains - 0.85 mol
then 25.0 mL should contain - 0.85 mol / 1000 mL x 25.0 mL = 0.0213 mol 
mass of KBr - 0.0213 mol x 119 g/mol = 2.53 g
mass of KBr that should be dissolved in 25.0 mL is 2.53 g

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A ground state hydrogen atom absorbs a photon of light having a wavelength of 92.05 nm. It then gives off a photon having a wave
vodka [1.7K]
Absorbed photon energy
Ea = hc/λ.. (Planck's equation)
Ea = hc / 92.05^-9m 

<span>Energy emitted
Ee = hc/ 1736^-9m </span>

Energy retained ..
∆E = Ea - Ee = hc(1/92.05<span>^-9 - 1/1736^-9) </span>
<span>∆E = (6.625^-34)(3.0^8) (1.028^7)
∆E = 2.04^-18 J </span>

<span>Converting J to eV (1.60^-19 J/eV)
 ∆E = 2.04^-18 / 1.60^-19
∆E = 12.70 eV </span>

<span>Ground state (n=1) energy for Hydrogen = - 13.60eV </span>

<span>New energy state = (-13.60 + 12.70)eV = -0.85 eV </span>

<span>Energy states for Hydrogen
En = - (13.60 / n²) </span>

n² = -13.60 / -0.85 = 16
n = 4
4 0
3 years ago
Plants get energy from the​
Rainbow [258]

Answer:

Plants need energy from the sun, water from the soil, and carbon from the air to grow. Air is mostly made of nitrogen, oxygen, and carbon dioxide. So how do plants get the carbon they need to grow? They absorb carbon dioxide from the air.

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4 0
2 years ago
Someone please help me figure this out!!
zavuch27 [327]

Answer: from what i can tell it looks like a heterogeneous mixture

Explanation:

heterogeneous is multiple different components, homogenous includes only the same component

7 0
3 years ago
Classify the four reactions that your group analyzed today as being either endothermic or exothermic
ArbitrLikvidat [17]
Chemical reactions are basically divided into two major classes depending on whether the reaction lose energy or gain energy from the environment during the course of the reaction. The two classes of reaction are exothermic and endothermic reaction.
An exothermic reaction is a type of reaction in which the reaction system lose energy to the environment and thus, the energy content of the reactants is more than that of the product formed. Because of this, the enthapyl change of an exothermic reaction is always negative. 
An endothermic reaction is a type of reaction in which the reaction system absorb energy from the environment. Thus, the energy contents of the products is always higher than that of the reactants and the enthapyl change of the reaction is always positive. During the course of the reaction, the reaction container is usually cold to the touch because energy is been absorbed from the environment.
4 0
3 years ago
ammonia gas is used as refrigerant 0.474 atm. Pressure is required to change 2000 cm3 sample of ammonia initially at 1.0 atm to
Andreas93 [3]

Answer: The pressure required is 0.474 atm

Explanation:

Boyle's Law: This law states that pressure is inversely proportional to the volume of the gas at constant temperature and number of moles.

P\propto \frac{1}V}   (At constant temperature and number of moles)

The equation is,

{P_1V_1}={P_2V_2}

where,

P_1 = initial pressure of gas = 1.0 atm

P_2 = final pressure of gas = ?

V_1 = initial volume of gas = 2000cm^3

V_2 = final volume of gas = 4.22dm^3=4220cm^3    (1dm^3=1000cm^3)

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

{1.0\times 2000}={P_2\times 4200}

P_2=0.474atm

The pressure required is 0.474 atm

5 0
3 years ago
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