The range in size of most atomic radii is approximately <span>5 × 10−21 m to 2 × 10−20 m. The rest of the choices do not answer the question above.</span>
A.) half - life of a radioactive substance is defined as the time during which concentration of the substance becomes half the initial value.
Well, the cause of a volcanic eruption is when the lower crust melts. This leads to the formation of magma. The volcano is an opening through which the magma is discharged. The rock inside the earth melts. This magma is diffused upwards through the volcano. If magma reaches the top of the volcano, it behaviour depends on viscosity. So what happens before a volcanic eruption is that the lower crust melts, causing the formation of magma, which is released through the volcano. Hope i helped.
Answer:
The answer is most likely A. Definite proportions
Explanation:
The Law of Definite proportions states that a given chemical compound always contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation.
The specific gravity of a sample is the ratio of the density of the sample with respect to one standard sample. The standard sample used in specific gravity calculation is water whose density is 1 g/mL. The solution having specific gravity 1.30 is the density of the sample that is 1.30 g/mL. Thus the weight of the 30 mL sample is (30×1.30) = 39 g.
Now the mass of the 10 mL of water is 10 g as density of water is 10 g/mL. Thus after addition the total mass of the solution is (39 + 10) = 49g and the volume is (30 + 10) = 40 mL. Thus the density of the mixture will be 
g/mL. Thus the specific gravity of the mixed sample will be 1.225 g/mL.
