The relative atomic mass of hydrogen is 1 and of carbon is 12. 12g of an unknown hydrocarbon (containing hydrogen and carbon only) was found to contain 9g of carbon. This is shown below. What is the value of x?

Achemistry student weighs out 0.306 g of citric acid (h3c6h5o7), a triprotic acid, into a 250 ml volumetric flask and dilutes to the mark with distilled water. he plans to titrate the acid with 0.1000 m naoh solution. calculate the volume of naoh solution the student will need to add to reach the final equivalence point. be sure your answer has the correct number of significant digits.