After completing her studies, in 1926 she began work as a researcher in theoretical Chemistry in the laboratories of the Faculty of the University of Zaragoza. Her research would later take her to other public and private research centers, such as the Escuela Industrial of Zaragoza, the Escuela Superior de Trabajo of Madrid, the Anstalt für Anorganische Chemie of the University of Basel (as a fellowship recipient of the Junta para Ampliación de Estudios e Investigaciones Científicas), and the National Institute of Physics and Chemistry (Instituto Nacional de Física y Química) of Madrid in the electrochemistry department (continuing and expanding upon the works she began in Switzerland and Germany, where she had gone to research electrochemistry as a fellow of the JAE). During her tenure at the INFQ, she published 11 articles about electrochemical research, and in particular, electrolytic analysis.
In 1929, Dr. Arnal Yarza became a member of the Spanish Society for Physics and Chemistry () for her distinguished research career in Spain and abroad.
While she worked at the laboratories of the Anstalt für anorganische Chemie in Basel, she studied under Friedrich Fichter, professor of inorganic chemistry and then vice-president of the International Union of Chemistry. Together they worked on the chemical oxidation of various metals, but specifically the creation of fluorine and of persulfates of zinc and lanthanum from the electrolysis of molten potassium biflouride. They published the results of their work in 1931 in the notable Swiss periodical Helvetica Chimica Acta. Arnal Yarza also researched chemical oxidation produced by the action of fluorine in gaseous states. She spent some time studying in the Technische Hochschule in Dresden thanks to a two-semester extension of her original scholarship from 1932.
After the Spanish Civil War began in Madrid, in 1937 Arnal Yarza left Spain and resided for a time in France. She later returned to the Spanish "National Zone" (). Throughout the war she was able to continue her research work without being sanctioned.
During the Spanish Civil War and the early years of Francos dictatorship, very few women, all unmarried, were allowed to participate in scientific research. While Jenara did not return to full-time research after the war, while teaching secondary school she continued to be interested in science and completed various works for the Consejo Superior de Investigaciones Científicas (CSIC), while she served at the teaching institute Instituto de Pedagogía San José de Calasanz. She collaborated in writing for the Boletín Bibliográfico del CSIC' journal, most notably in publications dedicated to primary school teachers published by of the Auxiliary Library of Education (Biblioteca Auxiliar de Educación).
She was the second woman to serve as the director of a department of physics and chemistry at a Spanish secondary school from 1930 onward.
In May 1947 Arnal Yarza obtained authorization to travel to London to attend the First Centennial of the Royal Society and the XI International Congress of Pure and Applied Chemistry. In December, the General Office of Secondary Education (Dirección General de Enseñanzas Medias) gave her permission to go on a trip to Japan as a delegate of the (Foreign) Exchange Section of CSIC. Upon her return to Spain, Arnal Yarza gave conferences and facilitated the exchange of publications by CSIC with Japanese universities and centers of advanced research. Later, she would return to Japan under the auspices of the CSIC for two years where she would advance her studies in chemistry.
In July 1953, she made a trip to attend the XIII International Congress of Pure and Applied Chemistry in Stockholm and Uppsala. That same year she began her last trip to Europe for research purposes, to attend the meeting of the International Committee of Electrochemical Thermodynamics and Kinetics in Vienna from September 28 to October 5, 1953.
Jenara Vicenta Arnal Yarza died suddenly on May 27, 1960, of a cerebral hemorrhage due to thrombosis. After her death, the Ministry of Education awarded her the distinguished honor of the Orden Civil de Alfonso X el Sabio.