Chemistry, 05.07.2020 01:01 Merida06

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Answer from: jennychen2518pbmirn

QUESTIONS !

1. Why might pesticides sprayed onto the fields reduce a bean crop?

A Pesticides damage plant leaves.

B Pesticides damage plant roots.

C Pesticides kill insects that feed on bean plants.

D Pesticides kill insects that pollinate bean plants.

2. What may cause the rapid growth of plants in a lake?

A excess fertilizers

B excess herbicides

C low water pH

D low water temperature

ANSWER !

1. (D) Pesticides kill insects that pollinate bean plants. 2. (B) Excess Herbicides

EXPLANATION !

1. When a field is sprayed with a pesticide, not all of the insects will die, and the ones that remain will produce offspring that will also be tolerant to the spray. This forces farmers to use more and different kinds of pesticides, so they can kill all of the insects that might destroy their crop.2. During periods of heavy rainfall, increased runoff brings more nutrients into a lake. These additional nutrients may be released from flooded soils or carried into the lake on silt or clay particles. Excess nutrients often boost plant growth, particularly algae or free-floating aquatic plants. PLEASE MARK AS BRAINLIEST

Answer from: Quest

part 1: the half-life of the element is 22 years.

part 2: it will take 132.02 year for the sample to decay from 308.0 g to 4.8125 g.

explanation:

part 1: there are two ways to determine the half life time.

first way: the half life time can be determined directly from its definition as it is the time required for the sample to decay to its half concentration.

from the data the initial concentration was 45.0 g and decayed to its half value (22.5 g) in 22.0 years.

second way: the radio active decay is considered first order reaction so we can use the laws of first order reactions.

k = (1/t) ln (a/a-x), where k is the rate constant of the reaction,

t is the time of the reaction

a is the initial concentration of the reactant

a-x is the remaining concentration at time (t)

a = 45.0 g the initial concentration at t = 0 year.

at t = 22 year, a-x = 22.5 g

then k = (1/22 year) ln (45.0 g/ 22.5 g) = 0.0315 year-1.

the half-life time (t1/2) = ln 2/ k = 0.693/ k =0.693/ 0.0315 = 22 years.

part 2:

using the same law k = (1/t) ln (a/a-x),

using the given data; a = 308.0 g and a-x = 4.8125 g and the calculated k from the part 1 (k = 0.0315 year-1)

t = (1/k) ln (a/a-x) = (1/0.0315) ln (308.0/ 4.8125) = 132.02 years

Answer from: Quest

it means there are 3 atoms of oxygen

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