What kind of spectra was analyzed to determine atomic
numbers of elements?

The kind of spectra used to measure the atomic number of elements is X-ray spectra.

The atomic number of elements is the number of protons in the nucleus of the element. According to the modern periodic law, the properties of elements is a periodic function of their atomic numbers.

In 1913, Mosely demonstrated that the atomic number of elements can be obtained from the X-ray spectra of elements. Using this method, he arranged the elements in order of increasing atomic number.

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Optical Atomic Spectroscopy

Explanation:

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the maximum mass of nh3 is nh3 in grams

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2