C describes plastics that can be recycled. Thermoplastic can be remolded and reheated after forming, whereas thermoset strengthens when heated
Answer: Number of molecules of hydrogen gas 
Explanation:
Number of moles of sodium =
According to reaction , 2 moles of sodium produces 1 mole of hydrogen gas , then 2.11 mol of sodium will= 
of hydrogen gas that is 1.05 moles of hydrogen gas.
Number of molecules = 
moles of substance
Moles of hydrogen gas formed = 1.05 moles
Number of molecules of hydrogen gas = 
moles of hydrogen gas
Number of molecules of hydrogen gas 
When it comes to ecosystems, a mountain, a river, and a cloud have more in common than you might think. Abiotic factors have specific and important roles in nature because they help shape and define ecosystems.
Biotic and Abiotic Factors
An ecosystem is defined as any community of living and non-living things that work together. Ecosystems do not have clear boundaries, and it may be difficult to see where one ecosystem ends and another begins. In order to understand what makes each ecosystem unique, we need to look at the biotic and abiotic factors within them. Biotic factors are all of the living organisms within an ecosystem. These may be plants, animals, fungi, and any other living things. Abiotic factors are all of the non-living things in an ecosystem.
Both biotic and abiotic factors are related to each other in an ecosystem, and if one factor is changed or removed, it can affect the entire ecosystem. Abiotic factors are especially important because they directly affect how organisms survive.
Examples of Abiotic Factors
Abiotic factors come in all types and can vary among different ecosystems. For example, abiotic factors found in aquatic systems may be things like water depth, pH, sunlight, turbidity (amount of water cloudiness), salinity (salt concentration), available nutrients (nitrogen, phosphorous, etc.), and dissolved oxygen (amount of oxygen dissolved in the water). Abiotic variables found in terrestrial ecosystems can include things like rain, wind, temperature, altitude, soil, pollution, nutrients, pH, types of soil, and sunlight.
The boundaries of an individual abiotic factor can be just as unclear as the boundaries of an ecosystem. Climate is an abiotic factor - think about how many individual abiotic factors make up something as large as a climate. Natural disasters, such as earthquakes, volcanoes, and forest fires, are also abiotic factors. These types of abiotic factors certainly have drastic effects on the ecosystems they encounter.
A special type of abiotic factor is called a limiting factor. Limiting factors keep populations within an ecosystem at a certain level. They may also limit the types of organisms that inhabit that ecosystem. Food, shelter, water, and sunlight are just a few examples of limiting abiotic factors that limit the size of populations. In a desert environment, these resources are even scarcer, and only organisms that can tolerate such tough conditions survive there. In this way, the limiting factors are also limiting which organisms inhabit this ecosystem.
