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1 year ago

Please help!

Chemistry

2 answers:

ANEK [815]1 year ago

8 0

Answer:

A- Physical, B- Chemical, C- chemical, D- Physical

Explanation:

A is physical because you can see it changing its form is changing.

B is Chemical because a new substance is formed creating the orange color of rust.

C is a Chemical reaction because it is being broken down so the banana itself is changing not just how we see it.

D is physical because we are just changing the shape/ size of the item, not anything to do with its substances.

motikmotik1 year ago

8 0

Answer:

a. physical change, it is reverse reversible since no new substance is created.

b.chemical change, The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust.

c. chemical change, Bananas contain compounds known as polyphenol oxidases and iron-containing chemicals. These chemicals react with oxygen to turn the fruit brown.

d. physical change, there is no new substance created, and there is no change in the original composition of wood.

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kogti [31]

Answer:

The molar mass of the unknown gas is $\mathbf{ 51.865 \ g/mol}$

Explanation:

Let assume that the gas is O2 gas

O2 gas is to effuse through a porous barrier in time t₁ = 4.98 minutes.

Under the same conditions;

the same number of moles of an unknown gas requires time t₂ = 6.34 minutes to effuse through the same barrier.

From Graham's Law of Diffusion;

Graham's Law of Diffusion states that, at a constant temperature and pressure; the rate of diffusion of a gas is inversely proportional to the square root of its density.

i.e

$R \ \alpha \ \dfrac{1}{\sqrt{d}}$

$R = \dfrac{k}{d}$ where K = constant

If we compare the rate o diffusion of two gases;

$\dfrac{R_1}{R_2}= {\sqrt{\dfrac{d_2}{d_1}}$

Since the density of a gas d is proportional to its relative molecular mass M. Then;

$\dfrac{R_1}{R_2}= {\sqrt{\dfrac{M_2}{M_1}}$

Rate is the reciprocal of time ; i.e

$R = \dfrac{1}{t}$

Thus; replacing the value of R into the above previous equation;we have:

$\dfrac{R_1}{R_2}={\dfrac{t_2}{t_1}}$

We can equally say:

${\dfrac{t_2}{t_1}}= {\sqrt{\dfrac{M_2}{M_1}}$

${\dfrac{6.34}{4.98}}= {\sqrt{\dfrac{M_2}{32}}$

$M_2 = 32 \times ( \dfrac{6.34}{4.98})^2$

$M_2 = 32 \times ( 1.273092369)^2$

$M_2 = 32 \times 1.62076418$

$\mathbf{M_2 = 51.865 \ g/mol}$

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