Please help me, I'm stuck and I don't know how to do it. How many atoms are there in 7.02 g Si ?

If 1.63 times 10 negative 4 of helium dissolves in 100.0g of water, what is the concentration in parts per million

In 2002, the rare earth elements mine in mountain pass, california was closed because

Consider the following reaction at equilibrium. 2co2 (g) 2co (g) + o2 (g) h° = -514 kj le châtelier's principle predicts that the equilibrium partial pressure of co (g) can be maximized by carrying out the reaction a. at high temperature and high pressure b. at high temperature and low pressure c. at low temperature and low pressure d. at low temperature and high pressure e. in the presence of solid carbon