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3 years ago

Which MOST CLOSELY identifies a theme in this passage?

Chemistry

1 answer:

Delicious77 [7]3 years ago

8 0

Answer:

Explanation:

It is the theme of the passage.

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Which star is the dimmest HELP PLEASE

Len [333]

Answer:

Bellatrix.

Explanation:

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2 years ago

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Given the equation Ca + H2O --> Ca(OH)2 + H2 how many grams of calcium will react completely with 10.0 grams of water? *

Yuki888 [10]

Answer: 11.0 g of calcium will react with 10.0 grams of water.

Explanation:

To calculate the moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}$

moles of $H_2O$

$\text{Number of moles}=\frac{10.0g}{18g/mol}=0.55moles$

The balanced chemical equation is:

$Ca+2H_2O\rightarrow Ca(OH)_2+H_2$

According to stoichiometry :

2 moles of $H_2O$ require = 1 mole of $Ca$

Thus 0.55 moles of $H_2O$ require= $\frac{1}{2}\times 0.55=0.275moles$ of $Ca$

Mass of $Ca=moles\times {\text {Molar mass}}=0.275moles\times 40g/mol=11g$

Thus 11.0 g of calcium will react with 10.0 grams of water.

3 0

3 years ago

Metals have high melting and boiling points and are often shiny and silvery. Which of the blocks are metals?

DanielleElmas [232]

Answer:

S and p blocks elements are considered metals while d-block elements are considered transition metals.

Explanation:

s-block consist of lithium, sodium, potassium, rubidium, cesium and francium metals.

All are these called alkali metals.

These metals have one valance electron.

These metals are soft and having low density.

They easily lose their one valance electron and form cation with +1 charge.

They have low melting points.

P- block elements includes beryllium, magnesium, calcium, strontium, barium, radium metals.

They are called alkaline earth metals.

All are these have two valance electrons.

They easily lose their valance electrons and form cation with charge of +2.

These metals are also very soft.

They form salt with halogens.

They are also very reactive metals.

8 0

3 years ago

A manufacturing plant has been found guilty of polluting the nearby river. This is _______ pollution.

dusya [7]

Answer:

the answer would be C: point source

Explanation:

because it specified the source of the pollution (manufacturing plant)

7 0

3 years ago

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Ethanol (c2h5oh) melts at -114Â°c. the enthalpy of fusion is 5.02 kj/mol. the specific heats of solid and liquid ethanol are 0.9

Nimfa-mama [501]

Answer: 4.18925 kJ heat is needed to convert 25.0 g of solid ethanol at -135 °C to liquid ethanol at -50°C.

Explanation:

Temperature of Solid $C_2H_5OH=-135^oC=138 K(0^oC=273K)$

Melting temperature of Solid $C_2H_5OH=114^oC=159 K$

Temperature of liquid $C_2H_5OH=-50^oC=223K$

Specific heats of solid ethanol = 0.97 J/gK

Specific heats of liquid ethanol = 2.3 J/gK

Heat required to melt the the 25 g solid $C_2H_5OH$ at 159 K

$\Delta T_1$ = 159 K - 138 K = 21 K

$Q_1=mc\Delta T= 25\times 0.97J/gK\times 21 K=509.25 J$

Heat required to melt and raise the temperature of $C_2H_5OH$ upto 223 K

$\Delta T_2$ = 223 K - 159 K = 64 K

$Q_2=mc\Delta T= 25\times 2.3J/gK\times 64 K=3680 J$

Total heat to convert solid ethanol to liquid ethanol at given temperature :

$Q_1+Q_2=509.25 J+3680 J=4189.25 J=4.18925 kJ$ (1kJ=1000J)

Hence, 4.18925 kJ of heat will be required to convert 25.0 g of solid ethanol at -135 °C to liquid ethanol at -50°C.

6 0

3 years ago