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3 years ago

Calculate the mass percent by volume of 42.6 g of glucose (C₆H₁₂O₆, MM = 180.2 g/mol) in 325 mL of solution.

Chemistry

1 answer:

expeople1 [14]3 years ago

4 0

Answer:

1.67 mol/L

Explanation:

(Mass of the component in the solution / Total mass of the solution) x 100

Other methods are:

Volume percentage:

Volume % of a component =

(Volume of the component/Total volume of the solution) x 100

Mass by volume percentage:

It is the mass of solute dissolved in 100 mL of the solution.

i.e. Mass by Volume percentage =

(Mass of solute in grams/Volume of solution in mL) x 100

Here's a point to be kept in mind :

Whenever we say mass or volume of the solution, you need to add the respective masses and volumes of ALL the components of the solution. Do NOT commit the error of taking the mass or volume of only the solute or solvent in the denominators of the above expressions.

The concentration of a solution is most of the time expressed as the number of moles of solute present in 1 Liter of the solution (also called molarity )

(There are also other ways to express concentration. Please follow this link. )

EXAMPLE:

(a) If 25 moles of NaCl are present in 100 L of a solution wherein H2O is the solvent, then the concentration of the solution is

100

0.25

mol⋅L

−

(b) What is the molarity of a solution prepared by dissolving 15.0 g of sodium hydroxide in enough water to make a total of 225 mL of solution?

Solution

Calculate the number of moles of solute present.

Moles of NaOH = 15.0 g NaOH ×

mol NaOH

40.00

g NaOH

= 0.375 mol NaOH

Calculate the number of litres of solution present.

Volume = 225 mL ×

1000

= 0.225 L soln

Divide the number of moles of solute by the number of litres of solution.

Molarity =

0.375

mol

0.225

= 1.67 mol/L

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How much (Q) heat is needed to melt 35 g of iodine? Hf = 61.7 J/g.

aev [14]

Taking into account the definition of calorimetry and latent heat, a heat of 2159.5 J is needed to melt 35 g of iodine.

<h3>Calorimetry</h3>

Calorimetry is the measurement and calculation of the amounts of heat exchanged by a body or a system.

<h3>Latent heat</h3>

Latent heat is defined as the energy required by a quantity of substance to change state.

When this change consists of changing from a solid to a liquid phase, it is called heat of fusion and when the change occurs from a liquid to a gaseous state, it is called heat of vaporization.

The heat Q that is necessary to provide for a mass m of a certain substance to change phase is equal to

Q = m×L

where L is called the latent heat of the substance and depends on the type of phase change.

<h3>Heat needed to melt iodine</h3>

In this case, you know:

m= 35 g
L=61.7 $\frac{J}{g}$

Replacing in the definition of latent heat:

Q= 35 g× 61.7 $\frac{J}{g}$

Solving:

Finally, a heat of 2159.5 J is needed to melt 35 g of iodine.

Learn more about calorimetry:

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8 0

2 years ago

Flourine is found to undergo 10% radioactivity decay in 366 minutes determine its halflife

yuradex [85]

Answer:

$\boxed{\text{2408 min}}$

Explanation:

The integrated rate law for radioactive decay is

$\ln\dfrac{N_{0}}{N_{t}} = kt$

1. Calculate the decay constant

$\begin{array}{rcl}\ln \dfrac{100}{90} & = & k \times 366\\\\1.054 & = & 366k\\\\k & = & \dfrac{1.054 }{366}\\\\k & = & 2.879 \times 10^{-4} \text{ min}^{-1}\\\end{array}\\\\$

2. Calculate the half-life

$t_{\frac{1}{2}} = \dfrac{\ln2}{k}\\\\t_{\frac{1}{2}} = \dfrac{\ln2}{2.879 \times 10^{-4} \text{ min}^{-1}} = \text{2408 min}\\\\\text{The half-life for decay is } \boxed{\textbf{2408 min}}$

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3 years ago

One compound that contributes to the "seashore smell" at beaches in Hawaii is dictyopterene D', a component of a brown edible se

Luba_88 [7]

Answer:

Explanation:

There are few simple rules in organic chemistry which a person must learn.

1. In predicting a structure from ozonolysis, number of oxygen present in products must be counted. In this particular example, there are 2+3+1 = 6 oxygen atoms are present in three molecules. This means that there should be at least three confirmed double bonds must be present in the molecule of Dictyopterene.

2. There are in total of 3+5+3 = 11 carbon atoms present, making 2^11 = 2048 possible structures for this particular structure. But since there are three double bonds present, this will reduce the number of possible structures as well.

3. Questions also says that when fully hydrogenated, the molecule generates Butylcycloheptane. That means that our base molecule is Butylcycloheptane and this molecule contains at least three double bonds.

So, first we draw the molecule of butylcycloheptane. After this, we think of were double bonds could be present. We do have the products. Let's make their structures first. I have also mentioned the possible breakup where the ozonolysis has occured by color code. You can see them in the reference image attached.

Part 1 out of 2: There is only one chiral carbon present in the molecule and have two possible isomers. Cis and Trans. Only one stereogenic carbon is present, that's why two possible isomers. Image attached.

7 0

3 years ago

This is a material that transmits most of the light that strikes to pass through and only a small amount of light is reflected o

inn [45]

Answer:

Optically Transparent

7 0

3 years ago

How much heat energy is required to melt 75g of ice at 0°C?

Mnenie [13.5K]

The enthalpy change for melting ice is called the entlaphy of fusion. Its value is 6.02 kj/mol. This means for every mole of ice we melt we must apply 6.02 kj of heat. We can calculate the heat needed with the following equation:

Q = N x ΔH

where:

Q = heat

N = moles

ΔH = enthalpy

In this problem we would like to calculate the heat needed to melt 35 grams of ice at 0 °C. This problem can be broken into three steps:

1. Calculate moles of water

2. multiply by the enthalpy of fusion

3. Convert kJ to J.

Step 1 : Calculate moles of water

$[ 75g ] x (\frac{1 mol}{18.02g} ) =$

Step 2 : Multiply by enthalpy of fusion

Q = N × ΔH = <em> [ Step 1 Answer ]</em> × 6.02 =

Step 3 : Convert kJ to J

$[ Step 2 Answer ] x (\frac{1000j}{1kJ} ) =$

Finally rounding to 2 sig figs (since 34°C has two sig figs) we get

Q Would Equal ____

4 0

3 years ago