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3 years ago

What is the main idea of the article, "Great Wall of China"?

Chemistry

1 answer:

grin007 [14]3 years ago

7 0

well, without the article, I'm guessing the main idea is about the Great Wall of China

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It is easier to push a sofa across a rough surface like carpet than a smooth surface like a hardwood floor.

Gelneren [198K]

False, pushing a sofa on a hardwood floor would be easier than on carpet.

3 0

3 years ago

1. An electric power plant uses energy from burning coal to generate steam at 450 °C. The plant is cooled by 20 °C water

kap26 [50]

Answer:

Explanation:

Efficiency of the electric power plant is $e=1-\frac{T_{2}}{T_{1}}$

Here Temperature of hot source $T_{1} = 450^{o}C=450+273=723 K$

and Temperature of sink $T_{1} = 20^{o}C=20+273=293 K$

Hence the efficiency is $e=1-\frac{293}{723}=0.5947=59.47%$

Now another formula for thermal efficiency Is

$e_{therm}=\frac{Q_{1}-Q_{2}}{Q_{1}}=\frac{W}{Q_{1}}$

Here QI is the of heat taken from source 100 MJ ; Q2 of heat transferred to the sink (river) to be found

W is the of work done and W = QI -Q2

Hence From $e_{therm}=\frac{Q_{1}-Q_{2}}{Q_{1}}=\frac{W}{Q_{1}}$

$W=e(Q_{1})=(0.5947)(100)=59.47MJ$

Hence the of heat transferred to the river Is $Q_{2} -W = (100 -59.47=40.53$

6 0

3 years ago

Are elements always transparent

Dmitry_Shevchenko [17]

No, the elements are not always transparent.

<u>Explanation:</u>

The elements become transparent when the light passes through those elements. Transparency is caused because of the transmission and the passing of the light waves through these elements.

But the metals do not become transparent even when the light waves pass through these metals. Metals do not become transparent because the refractive index in them is very big.

8 0

3 years ago

A. Calculate the empirical formula of a molecule with percent compositions: 55.3% potassium (K), 14.6% phosphorus (P), and 30.1%

Otrada [13]

The way you calculate the empirical formula is to firstly assume 100g. To find each elements moles you take each elements percentage listed, times it by one mole and divide it by its atomic mass. (ex: moles of K =55.3g x 1 mole/39.1g, therefore there is 1.41432225 moles of Potassium) Once you’ve completed this for every element you list each elements symbol beside it’s number of moles and divide by the smallest number because it can only go into its self once. After you’ve done this, you’ve found your empirical formula, which is the simplest whole number ratio of atoms in a compound. I’ve added an example of a empirical question I completed last semester :)

6 0

3 years ago

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Which of the following groups of subjects are categorized under natural science?

Lesechka [4]

Answer:

i guess b is the answer.hope it will help

8 0

3 years ago

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