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3 years ago

Select the items that describe a chemical property below. Choose THREE correct answers.

Chemistry

1 answer:

FrozenT [24]3 years ago

8 0

Answer:

2:A handwarmer gets warm when it is opened and exposed to air.

3:Propane ignites to heat a grill.

4:Cotton is dyed red to make a dress.

Explanation:

The definition of a chemical property is when a property of characteristic of a substance that is observed during a reaction in which a chemical has been changed

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What is the atomic number and mass number of calcium ?

solniwko [45]

Answer:

Calcium has an Atomic number of 20 and Atomic mass of 40.078 u

Hope this helps!

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2 years ago

If a concentration of 10 fluorescent molecules per μm2of cell membrane is needed to visualize a cell under the microscope, how m

lara [203]

Answer : Total molecules that will be needed to visualize a single egg will be 78500 molecules of dye.

Explanation : As a single egg cell has an approximately diameter of 100 μm.

We can use this formula to calculate area of the cell membrane;

A = π $(100)^{2} / 4$ ;

We can take π as 3.14 and we get;

A = 3.14 X $(100)^{2} / 4$

Soving we get;

A = 7850 μ $m^{2}$

Here we have to calculate the amount of dye molecules which will be needed for 10 fluorescent molecules / μ $m^{2}$ but;

here 1 μ $m^{2}$ = 7850 μ $m^{2}$ dye molecules.

Therefore, 10 fluorescent molecules will need;

7850 X 10 = 78500 molecules of dye.

Therefore, the answer is 78500 molecules of dye.

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3 years ago

After stirring the sugar you added to some hot tea, the sugar disappears but the tea tastes sweet.

kirza4 [7]

Chemical Change because if it would be a physical change the physic of the tea would look different but it doesn’t

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3 years ago

Cual es la temperatura de congelacion del agua

Sergio039 [100]

La temperatura de congelación del agua es 0 grados centígrados.

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3 years ago

Phosphoric acid, which is commonly used as rust inhibitor, food additive and etching agent for dental and orthopedic use, can be

Sphinxa [80]

Answer:

$P_4_{(I)}+5O_2_{(g)}+6H_2O_{(l)}\rightarrow +4H_3PO_4_{(l)}$

Explanation:

The first step is:

$P_4_{(I)}+5O_2_{(g)}\rightarrow 2P_2O_5_{(g)}$

Second step is:

$P_2O_5_{(g)}+3H_2O_{(l)}\rightarrow 2H_3PO_4_{(l)}$

Multiplying second step by 2, and adding both the steps, we get that:

$P_4_{(I)}+5O_2_{(g)}+2P_2O_5_{(g)}+6H_2O_{(l)}\rightarrow 2P_2O_5_{(g)}+4H_3PO_4_{(l)}$

Cancelling common species, we get that:

$P_4_{(l)}+5O_2_{(g)}+6H_2O_{(l)}\rightarrow +4H_3PO_4_{(l)}$

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3 years ago