Answer:
C. Lithium
Explanation:
I Goo gled it and I think that's right.
After 3 half life periods you would have 5 grams of krypton left because half of 40 is 20 half of 20 is 10 and half of 10 is 5
Answer:
A) positive; added
Explanation:
Based on the reaction:
2NaHCO3(s) + 129kJ → Na2CO3(s) + H2(g) + CO2(g)
<em>2 moles of NaHCO3 requires 129kJ to produce 1 mole of Na2CO3, 1 mole of H2 and 1 mole of CO2.</em>
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That means, the energy must be added being, thus, an exothermic reaction. The exothermic reactions have ΔH >0.
Thus, right answer is:
A) positive; added
The substance which has definite composition with definite physical and chemical properties is said to be pure substance. These substances are not separated by the different physical techniques such as filtration, distillation, evaporation etc.
The clear water pumped from a deep aquifer is a pure substance because water is a pure compound which consist of constant single type of atoms or group of atoms and water has specific value of boiling and melting point. Water is also not separated into units or constituents by physical technique.
Hence, clear water pumped from a deep aquifer is a pure substance.
