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3 years ago

Why was 1990 an important year regarding air quality?

Chemistry

1 answer:

Rus_ich [418]3 years ago

7 0

Answer:

The United States took first steps to keep the air clean.

Explanation:

The US environmental protection agency was created in the year 1970 so this option is wrong.

November 15, 1990 however was a milestone in keeping the air clean, the signing f the amendments, the amendments set the stage for protecting the ozone layer, improving air quality and visibility.

The correct option is option A; The United States took first steps to keep the air clean.

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2 HBr(g)+O2(g)—>H2O2(g)+Br2(g)

MrRissso [65]

Answer:

Explanation:

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3 years ago

Marcus measured the masses and volumes of samples of four different substances, and he calculated their densities. The table sho

Zina [86]

Given:

Calculated density values-

Aluminum = 2.7 g/cm3

Copper = 9.0 g/cm3

Iron = 7.9 g/cm3

Titanium = 4.8 g/cm3

Unknown sample mass = 9.5 g

Sample volume = 2.1 cm3

To determine:

The identity of the unknown sample

Explanation:

'Density' is a physical parameter which can be used to identify the nature of the unknown substance.

Density = Mass/Volume

For the unknown sample

Density = 9.5 g/2.1 cm3 = 4.52 g/cm3

This matches closely with the calculated density of titanium

Ans: The unknown substance is made of titanium

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3 years ago

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Dvinal [7]

Answer:

Parallel Circuit

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3 years ago

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ivann1987 [24]

They are eaten by Tertiary consumers

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3 years ago

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Given 3.4 grams of x compound with a molar mass of 85 g and 4.2 grams of y compound with a molar mass of 48 g How much of compou

Ulleksa [173]

Answer:

$4.36~g~XY$

Explanation:

In this case, we can start with the reaction:

$2X + Y_2~->~2XY$

If we check the reaction, we will have 2 X and Y atoms on both sides. So, the reaction is balanced. Now, the problem give to us two amounts of reagents. Therefore, we have to find the limiting reagent. The first step then is to find the moles of each compound using the molar mass:

$3.4~g~X\frac{1~mol~X}{85~g~X}=0.04~mol~X$

$4.2~g~Y_2\frac{1~mol~Y_2}{48~g~Y_2}=0.0875~mol~Y_2$

Now, we can divide by the coefficient of each compound (given by the balanced reaction):

$\frac{0.04~mol~X}{1}=~0.04$

$\frac{0.0875~mol~Y_2}{2}=0.04375$

The smallest value is for "X", therefore this is our limiting reagent. Now, if we use the molar ratio between "X" and "XY" we can calculate the moles of XY, so:

$0.04~mol~X\frac{2~mol~XY}{2~mol~X}=0.04~mol~XY$

Finally, with the molar mass of "XY" we can calculate the grams. Now, we know that 1 mol X = 85 g X and 1 mol $Y_2$ = 48 g $Y_2$ (therefore 1 mol Y = 24 g Y). With this in mind the molar mass of XY would be 85+24 = 109 g/mol. With this in mind:

$0.04~mol~XY\frac{109~g~XY}{1~mol~XY}=4.36~g~XY$

I hope it helps!

6 0

3 years ago