Unicellular organisms are so small that you usually need a telescope to see them.

Does rapidly cooled rock contain small crystals?

Lisa [10]

I believe they do, yes.

3 0

3 years ago

Which of the following radiations consists of a helium nucleus emitted by some radioactive substances? Alpha radiation Beta radi

erica [24]

Answer: Alpha radiation

Explanation: Alpha decay : When a larger radioactive nuclei decays into smaller nuclei by releasing alpha radiation, the mass number and atomic number is reduced by 4 and 2 units respectively.

$_Z^A\textrm{X}\rightarrow _{Z-2}^{A-4}Y+_2^4\textrm{He}$

Beta decay : When a larger radioactive nuclei decays into smaller nuclei by releasing beta radiation, the atomic number is increased by 1 unit.

$_Z^A\textrm{X}\rightarrow _{Z+1}^{A}Y+_{-1}^0e$

Gamma decay : When a larger radioactive nuclei decays into smaller nuclei by releasing gamma radiation, the mass number remains same.

$_Z^A\textrm{X}^*\rightarrow _Z^A\textrm{X}+_0^0\gamma$

5 0

3 years ago

A cube made of an unknown material has a height of 9 cm. The mass of this cube is 3,645 grams.

kvasek [131]

Answer:

v=9*9*9=729 ml

3645/729= 5g/cm 3

8 0

3 years ago

Which of the following below is the complete ionic equation of the reaction: Calcium nitrate and sodium sulfide solutions react

3241004551 [841]

To find the net ionic equation we must first write the balanced equation for the reaction. We must bear in mind that the reagents Ca(NO3)2 and Na2S are in the aqueous state and as product we will have CaS in the solid state, since it is not soluble in water and NaNO3 in the aqueous state.

The balanced equation of the reaction will be:

$Ca(NO_3)_{2(aq)}+Na_2S_{(aq)}\rightarrow CaS_{(s)}+2NaNO_{3(aq)}$

Ca(NO3)2(aq) + → Ca(aq) + 2Na(s)NO3Now, c(aq)ompounds in the aqueous state can be written in their ionic form, so the reaction will transform into:Na2S +

$Ca_{(aq)}^{2+}+2(NO_3)_{(aq)}^-+2Na_{(aq)}^++S_{(aq)}^{2-}\operatorname{\rightarrow}CaS_{(s)}+2Na_{(aq)}^++2NO^-_{3(aq)}$

So, the answer will be option A

5 0

1 year ago

Fill in the blanks.

ANTONII [103]

Answer:GASEOUS, LOWERING ,EMITTED AS HEAT, DOWN,DO NOT RELEASE,DECREASES,NEGATIVE.

Explanation: Filling the blanks gives

Lattice energy is associated with forming a crystalline lattice of alternating cations and anions from the _GASEOUS___________ ions.

Because the cations are positively charged and the anions are negatively charged, there is a LOWERING of potential- as described by Coulomb's law-when the ions come together to form a lattice energy.That energy is EMITTED AS HEAT when the lattice forms.

As the ionic radii increases as you move DOWN a group, ions cannot get as close to each other and therefore DO NOT RELEASE as much energy when the lattice forms. Thus the lattice energy DECREASES (becomes less) NEGATIVE as the radius increases.

The above gives the definition of Lattice Energy and how it relates to atomic and ion charge.

6 0

3 years ago