How much would you need to weigh out in order to have 0.2moles of magnesium atoms?

How does concentration affect reaction rate

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?

What volume of a 0.0606 m solution of strontium bromide is needed to obtain 0.340 mol of the compound? question 42 options: a)5.61 l b) 3.4 l c) 600 ml d) 1 l e) 178 ml