It's fairly easy to generate a significant yield of hydrogen gas simply by reacting zinc metal with $\ce{HCl}$ or aluminum with $\ce{NaOH}$ solution. But is there a simple and inexpensive chemical reaction that generates a significant yield of pure nitrogen gas?
Answer
Per Wikipedia, we have this laboratory method:
$$\ce{NH4Cl(aq) + NaNO2(aq) → N2(g) + NaCl(aq) + 2 H2O (l)}$$
Also per Wikipedia, this method generates small quantities of impurities of $\ce{NO}$ and $\ce{HNO3}$, which can be eliminated by passing the gas through potassium dichromate $\ce{(K2Cr2O7)}$ dissolved in sulfuric acid $\ce{(H2SO4)}$
Both ammonium chloride and sodium nitrite are reasonably available chemicals, and the other products (table salt and water) are undeniably safe. Sulfuric acid might a bit tougher to get depending on where you live, and potassium dichromate will be the most difficult given that the use of hexavalent chromium is discouraged (and you should research procedures to reduce the $\ce{Cr2O7^{-2}}$ to $\ce{Cr2O3}$). But otherwise, this looks like the best approach.
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