Cesium-135 has a half life of approximately 30 years. If a sample, which originally contained 8 mg, is found to contain 0.25 mg of Cs-135, how old is the sample?
half-life have occurred so the sample is ___ hours.

The sample has 150 years, 1314000 hours

Explanation:

The element decay follows the first order kinetics law:

ln[Cs-135] = -kt + ln [Cs-135]₀ (1)

Where [Cs-135] is concentration after t time, k is rate constant in time, and [Cs-135]₀ is initial concentration

Half-life formula is:

30 years = ln2 / k

k = 0.0231 years⁻¹

Using rate constant in (1):

ln[0.25mg] = -0.0231 years⁻¹×t + ln [8mg]

-3.466 = -0.0231 years⁻¹×t

150 years = t

The sample has 150 years

In hours:

150years × (365days / 1year) × (24hours / 1day) = 1314000 hours

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation:

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

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