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nikdorinn [45]
3 years ago
8

The insecticide DDT was introduced in the 1950s, and the rates of malaria dropped significantly. DDT was later found to be toxic

to birds and other animals, and it was discontinued in 1964.
As a result, rates of malaria began to rise. How can the effects of DDT on society be characterized?
Chemistry
2 answers:
coldgirl [10]3 years ago
5 0
Both positive and negative . {c}
boyakko [2]3 years ago
5 0

The correct answer for above statement is:

both positive and negative .

Explanation:

DDT should be used "with caution" in fighting malaria,

DDT (dichlorodiphenyltrichloroethane) was condemned in Britain in 1986 and prevented as a pesticide worldwide under the Stockholm Convention in 2001 after it was determined to be hazardous to wildlife and the environment.

The 15 environmental health specialists, who evaluated almost 500 health studies, decided that DDT "should be used with caution, only when needed, and when no other adequate, safe and affordable dilemmas are locally accessible.

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How many pounds of ice are required to absorb 4900 kJ of heat as the ice melts? The heat of fusion of water is 0.334 kJ/g.
Goshia [24]

Answer:

m = 32.34 pounds of ice.

Explanation:

In this case we need to use the following expression of heat:

q = m * ΔHf   (1)

Where:

q: heat absorbed in J or kJ

m: mass of the compound in g

ΔHf: heat of fusion of the water in kJ/g

We are asked to look for the mass of ice in pounds, so after we get the grams, we need to convert the grams to pounds, using the following conversion:

1 pound --------> 453.59 g   (2)

So, we have the heat and heat of fusion, from (1) let's solve for the mass, and then, using (2) the conversion to pounds:

q = m * ΔHf  

m =  q / ΔHf

m = 4900 / 0.334 = 14,670.66 g of ice

Now, the conversion to pounds:

m = 14,670.66 g * 1 pound/453.59 g

<h2>m = 32.34 pounds of ice.</h2>

Hope this helps  

5 0
3 years ago
The progress of the reaction:
Blababa [14]

Answer:

The Equilibrium constant K is far greater than 1; K>>1

Explanation:

The equilibrium constant, K, for any given reaction at equilibrium, is defined as the ratio of the concentration of the products raised to their stoichiometric coefficients divided by the concentration of reactants raised to their stoichiometric coefficients.

It tells us more about how how bigger or smaller the concentration of products is to that of the reactants when a reaction attains equilibrium. From the given data, as the color of the reactant mixture (Br2 is reddish-brown, and H2 is colourless) fades, more of the colorless product (HBr is colorless) is being formed as the reaction approaches equilibrium. This indicates yhat the concentration of products becomes relatively higher than that of the reactants as the reaction progresses towards equilibrium, the equilibrium constant K, must be greater than 1 therefore.

6 0
3 years ago
3 points Given 0.65 moles KNO3: (a) Convert to grams (b) Convert to particles. <br>​
Vlad [161]

Answer: Convert to grams

Explanation:

8 0
3 years ago
Please help
lisabon 2012 [21]

Answer:

There are 2 hydrogen atoms, one magnesium atom, and 5 atoms in total.

Explanation:

We are given a compound in formula form. To make things easier to understand, we can first convert this to the name of the compound.

  • When a compound contains one or more elements in parentheses, these are usually a <u>polyatomic ion</u>.
  • Polyatomic ions are ions made up of two or more elements with a positive or negative charge over the entire ion. Commons examples of these NH₄⁺ (ammonia) and HCO₃⁻ (bicarbonate).
  • You can combine metals with polyatomic ions to create commonly known compounds, such as baking soda. The chemical name for baking soda is sodium bicarbonate, so we can combine Na (sodium) with HCO₃⁻ (bicarbonate) and create sodium bicarbonate: NaHCO₃.

This compound is one magnesium atom bonded to two hydroxide ions.

  • Hydroxide is the compound between one hydrogen atom and one oxygen atom. The compound overall adopts a negative charge of 1.
  • If we have one hydrogen atom and one oxygen atom, the most electronegative atom is written first in chemical formulas. Therefore, the symbol for Oxygen (O) goes first.
  • Then, write in the hydrogen atom directly after the O symbol: OH.
  • Finally, since we have a negative charge on the ion, we need to play a negative sign as a superscript for the compound. Therefore, this becomes OH⁻.

Now, we need to determine the charge on the Magnesium atom which is determined from the amount of valence electrons the atom has.

  • On a periodic table, the symbol for Magnesium is Mg and this element has 2 valence electrons.
  • In order to fulfill the Octet Rule, the It is more likely to give up 2 electrons to a nonmetal than it is to gain 6, so we can safely assume that the charge is ²⁺.
  • We need to use the criss-cross technique to transfer the charges between the element and the ion, so the negative 1 charge goes to the Mg, which does not appear (negative 1 or positive 1 are implied) and since the magnesium has a charge of positive 2, this is the subscript for the hydroxide ion.
  • Therefore, our compound becomes Mg(OH)₂, and we have labeled this as magnesium hydroxide.

Now, to the number of atoms:

  • The new charge on Mg is 1-, so there is only one atom of Mg.
  • The charge is 2+ on the OH ion, so there are two atoms of H and two atoms of O.
  • Two atoms of oxygen, two atoms of hydrogen, and one atom of magnesium add up to be five atoms in total.
3 0
3 years ago
Por que el petroleo es un no recurso renovable
mote1985 [20]

Answer:

Por ejemplo, el petróleo o el carbón son ejemplos de recursos no renovables porque, aunque se forman mediante un proceso natural, este necesita demasiado tiempo. ... Esos combustibles fósiles provienen de materia orgánica, pero tardan cientos de miles de años en producirse.

3 0
3 years ago
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