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2 years ago

Radium-221 has a half-life of 30 sec. How long will it take for 96% of a sample to decay?

1 answer:

monitta2 years ago

3 0

We can calculate how long the decay by using the half-life equation. It is expressed as:

A = Ao e^-kt

where A is the amount left at t years, Ao is the initial concentration, and k is a constant.
From the half-life data, we can calculate for k.

1/2(Ao) = Ao e^-k(30)
k = 0.023

0.04Ao = Ao e^0.023(t)
t = 140 sec

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7.Calculate the volume of nitrogen that reacts with 12dm3 of hydrogen with the volume of both gases measured at rtp:

marta [7]

Answer:

4.03dm³

Explanation:

The reaction expression is given as:

3H₂ + N₂ → 2NH₃

Volume of hydrogen = 12dm³

AT rtp:

1 mole of gas occupies volume of 22.4dm³

x mole of hydrogen will occupy a volume of 12dm³

Number of moles of hydrogen = $\frac{12}{22.4}$ = 0.54mole

From the balanced reaction equation:

3 mole of hydrogen gas combines with 1 mole of Nitrogen gas

0.54 mole of hydrogen as will therefore combine with $\frac{0.54}{3}$ = 0.18moles of nitrogen gas

Since ;

1 mole of gas occupies a volume of 22.4dm³

0.18moles of Nitrogen gas will occupy 0.18 x 22.4 = 4.03dm³

6 0

2 years ago

What is the kinetic evidence for SN1 reaction

inn [45]

Answer:

In doubling the concentration of the alkyl halide, the reaction rate also increases two-fold. However, doubling the concentration of the nucleophile does not in any way alter the reaction rate. Thus, the reaction rate is proportional only to the alkyl halide's concentration.

7 0

2 years ago

Ammonia and oxygen react to produce nitric oxide and water. Which of the following chemical equations describes this reaction an

aksik [14]

Answer:

Option B. 4NH3(g) + 5O2(g) —> 4NO(g) + 6H2O(g)

Explanation:

The reaction between ammonia, NH3 and oxygen, O2, will produce nitric oxide and water as shown below:

NH3(g) + O2(g) —> NO(g) + H2O(g)

Now, let us balance the equation.

This is illustrated below:

NH3(g) + O2(g) —> NO(g) + H2O(g)

There are 3 atoms of H on the left side and 2 atoms on the right side. It can be balance by putting 4 in front of NH3 and 6 in front of H2O as shown below:

4NH3(g) + O2(g) —> NO(g) + 6H2O(g)

There are 4 atoms of N on the left side and 1 atom on the right side. It can be balance by putting 4 in front of NO as shown below:

4NH3(g) + O2(g) —> 4NO(g) + 6H2O(g)

Now, the are 2 atoms of O on the left side and a total of 10 atoms on the right side. It can be balance by putting 5 in front of O2 as shown below:

4NH3(g) + 5O2(g) —> 4NO(g) + 6H2O(g)

Now, we can see that the equation is balanced.

Therefore, option B gives the balanced chemical equation for the reaction.

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2 years ago

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Kamila [148]

Answer:

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Explanation:

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