Problem: The X-ray crystal density method is primarily a method for determining the Avogadro constant NA but as the Avogadro constant is related to the Planck constant it also determines a value for h. The principle behind the method is to determine NA as the ratio between the volume of the unit cell of a crystal, measured by X-ray crystallography, and the molar volume of the substance. Crystals of silicon are used, as they are available in high quality and purity by the technology developed for the semiconductor industry. The unit cell volume is calculated from the spacing between two crystal planes referred to as d220. The molar volume Vm(Si) requires a knowledge of the density of the crystal and the atomic weight of the silicon used. The Planck constant is given by
How is unit cell volume calculated?
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Answer: from the spacing between two crystal planes referred to as d220


Problem: According to 16th-century mystic Rabbi Elijah of Chelm, Ashkenazi Jews lived in Jerusalem during the 11th century. The story is told that a German-speaking Palestinian Jew saved the life of a young German man surnamed Dolberger. So when the knights of the First Crusade came to siege Jerusalem, one of Dolberger's family members who was among them rescued Jews in Palestine and carried them back to Worms to repay the favor. Further evidence of German communities in the holy city comes in the form of halakhic questions sent from Germany to Jerusalem during the second half of the 11th century.
Mystic Rabbi Elijah of Chelm is from what century?
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Answer: 16th-century


Problem: Presbyterianism first officially arrived in Colonial America in 1703 with the establishment of the first Presbytery in Philadelphia. In time, the presbytery would be joined by two more to form a synod (1717) and would eventually evolve into the Presbyterian Church in the United States of America in 1789. The nation's largest Presbyterian denomination, the Presbyterian Church (U.S.A.) – PC (USA) – can trace their heritage back to the original PCUSA, as can the Presbyterian Church in America (PCA), the Orthodox Presbyterian Church (OPC), the Bible Presbyterian Church (BPC), the Cumberland Presbyterian Church (CPC), the Cumberland Presbyterian Church in America the Evangelical Presbyterian Church (EPC) and the Evangelical Covenant Order of Presbyterians (ECO).
When did America arrive in Presbyterianism?
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Answer:
unanswerable