Ammonia gas occupies a volume of 2,725ml at a pressure of 701 kPa. What volume would it occupy at 101 kPa?

A sample contains 2.2 g of the radioisotope niobium-91 and 15.4 g of its daughter isotope, zirconium-91. how many half-lives hav

dybincka [34]

Answer: 3

Explanation: This is a radioactive decay and all the radioactive process follows first order kinetics.

Equation for the reaction of decay of $_{19}^{40}\textrm{K}$ radioisotope follows:

$Moles of zirconium=\frac{\text{Given mass}}{\text{Molar mass}}=\frac{15.4}{91}=0.17moles$

$Moles of niobium=\frac{\text{Given mass}}{\text{Molar mass}}=\frac{2.2}{91}=0.024moles$

$_{41}^{91}\textrm{Nb}\rightarrow _{40}^{91}\textrm{Zr}+_{+1}^0e$

By the stoichiometry of above reaction,

1 mole of $_{40}^{91}\textrm{Zr}$ is produced by 1 mole $_{41}^{91}\textrm{Nb}$

So, 0.17 moles of $_{40}^{91}\textrm{Zr}$ will be produced by = $\frac{1}{1}\times 0.17=0.17\text{ moles of }_{40}^{91}\textrm{Nb}$

Amount of $_{82}^{212}\textrm{K}$

decomposed will be = 0.17 moles

Initial amount of $_{40}^{91}\textrm{Nb}$ will be = Amount decomposed + Amount left = (0.17 + 0.024)moles =0.194 moles

$a=\frac{a_o}{2^n}$

where,

a = amount of reactant left after n-half lives = 0.024

$a_o$ = Initial amount of the reactant = 0.194

n = number of half lives= ?

Putting values in above equation, we get:

$0.024=\frac{0.194}{2^n}$

$n=3$

Therefore, 3 half lives have passed.

3 0

2 years ago

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How many molecules are there in 9.34 grams of LiCL

julia-pushkina [17]

Assuming the question refers to LiCl (Lithium chloride) which has a molecular weight 42.39. Avogadro's constant states there are 6.022 141 79x1023 molecules per mole 9.34 g LiCl is 9.34/42.39 mole (0.220 mole) LiCl 
The number of molecules is therefore 6.022 141 79x1023x 0.220 =1.326x1023 molecules

7 0

1 year ago

An ion with 5 protons, 6 neutrons and a charge of 3+ has an atomic number of ____.

Umnica [9.8K]

Answer:An ion with 5 protons, 6 neutrons and a charge of 3+ has an atomic number of 5

Explanation:

3 0

2 years ago

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Heavy nuclides with too few neutrons to be in the band of stability are most likely to decay by what mode?

Margarita [4]

Answer:

Positron emission

Explanation:

Positron emission involves the conversion of a proton to a neutron. This process increases the mass number of the daughter nucleus by 1 while its atomic number remains the same. The new neutron increases the number of neutrons present in the daughter nucleus hence the process increases the N/P ratio.

A positron is usually ejected in the process together with an anti-neutrino to balance the spins.

6 0

2 years ago

Select the correct answer. A student places a sample of white sodium bicarbonate powder in a test tube and heats it. The student

inessss [21]

Answer is: D. It is not sodium bicarbonate.

Balanced chemical reaction of heating sodium bicarbonate: 2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O.

This is chemical change (chemical reaction), because new substances are formed (sodium carbonate, carbon(IV) oxide and water), the atoms are rearranged, so there is no sodium bicarbonate (NaHCO₃) in the test tube.

8 0

2 years ago