7.15g of Na2Co3.xH2O is dissolved in 250cm^3 of distilled water to form 0.10mol/dm^3.The entire solution was reacted with HCL to produce NaCl, H2O and 8960cm^3 of CO2 gas at stp in a beaker. Calculate 1.the contentration of Na2CO3.xH2O in g/dm^3
2.the molar mass of Na2CO3.xH2O

Although respiratory organs vary across different organisms, they all contain respiratory surfaces that have a large surface area and are extremely thin. explain why having an extremely thin respiratory surface with a large surface area is advantageous for the process of gas exchange

Stage in which a typical star has completely stopped fusion

Which fact represents evidence for the big bang theory?