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3 years ago

What does the term chemistry mean?

Chemistry

1 answer:

Elenna [48]3 years ago

7 0

the branch of science that deals with the identification of the substances of which matter is composed

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A forensic chemist is given a white powder for analysis. She dissolves 0.50 g of the substance in 8.0 g of benzene. The solution

Sholpan [36]

Answer:

The given compound cannot be cocaine.

Explanation:

The chemist can comment on the nature of compound being cocaine or not from the depression in freezing point.

Depression in freezing point of is related to molality as:

Depression in freezing point = Kf X molality

Where

Kf = cryoscopic constant = 4.90°C/m

depression in freezing point = normal freezing point - freezing point of solution

depression in freezing point = 5.5-3.9 = 1.6°C

1.6°C = 4.90 X molality

$molality=\frac{1.6}{4.90} = 0.327 m$

we know that:

$molality=\frac{moles}{mass of solvent(kg)}=\frac{moles}{0.008kg}$

therefore

moles = 0.327X0.008 = 0.00261 mol

$moles=\frac{mass}{molarmass}$

$molarmass=\frac{mass}{moles}=\frac{0.50}{0.00261}= 191.57g/mol$

The molar mass of cocaine is 303.353

So the given compound cannot be cocaine.

3 0

3 years ago

Define the chemical reaction?

Goshia [24]

Answer:

HOPE IT HELPED U ....

Explanation:

Chemical reaction is a process that involves rearrangement of the molecular or ionic structure of a substance, as distinct from a change in physical form or a nuclear reaction.

5 0

3 years ago

Read 2 more answers

The heat of fusion for a substance is 122 joules per gram. How many joules of heat are need to melt 7.50 grams of this substance

daser333 [38]

<h3>Answer:</h3>

915 Joules

<h3>Explanation:</h3>

The heat of fusion is the heat that is required to convert a given mass of a substance from solid state to liquid state without change in temperature.
In this case, we are given specific heat of a substance as 122 joules per gram
It means that amount of heat equivalent to 122 joules is required to change 1 gram of the substance from solid state to liquid state.

Therefore, we can determine the amount of heat needed to change 7.5 grams of the substance from solid to liquid state.

1 g = 122 Joules

7.5 g = ?

= 122 × 7.5

= 915 Joules

Thus, 7.5 g of the substance at its melting point will require 915 Joules of heat to melt.

4 0

3 years ago

Name 5 things that the periodic table includes about 1 atom for each element:

olganol [36]

Answer:

They are listed below

Explanation:

The 5 things that the periodic table includes are;

1. Name of the element

2. The symbol of the element

3. Atomic number of the element

4. Relative atomic mass

5. Electron configuration

5 0

3 years ago

Calculate the average reaction rate expressed in moles h2 consumed per liter per second

djyliett [7]

Answer:

Average rate of reaction expressed in moles H₂ consumed per liter per second = 0.0025 M/s = 0.0025 mol/L.s

Explanation:

The complete, correct Question, is presented in the attached image to this answer.

The average rate of reaction in terms of the reactant is defined as the total amount of reactant consumed over a period of time divided by total period of time.

Mathematically,

Average rate of reaction = (change in concentration of H₂ over a period of time) ÷ (total period of time)

Average rate of reaction = (-ΔC)/(Δt)

The minus sign is there because the concentration of reactants reduce with time.

change in concentration of H₂ = -ΔC

= -(0.02 - 0.03) = 0.01 M

Time = Δt = 4 - 0 = 4.0 s

Average rate of reaction = (0.01/4) = 0.0025 M/s

We could solve for the average rate of reaction expressed in moles Cl₂ consumed per liter per second

change in concentration of Cl₂ = -ΔC

= -(0.04 - 0.05) = 0.01 M

Time = Δt = 4 - 0 = 4.0 s

Average rate of reaction = (0.01/4) = 0.0025 M/s = 0.0025 mol/L.s

Hope this Helps!!!

8 0

3 years ago