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3 years ago

What makes up nearly all of the atom's mass?

Chemistry

2 answers:

VMariaS [17]3 years ago

7 0

Sum of the number of protons and neutrons, which is the nucleus

Ber [7]3 years ago

5 0

Answer:

The Nucleus

Explanation:

The nucleus of an atom contains both the protons (positively charged particles) and the neutrons (particles with no charge) - these two set of particles present in the nucleus of an atom determines the mass of an atom. Hence, atomic mass is the sum of the number of protons and number of neutrons present in the nucleus of an atom.

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What mass (in g) of NH3 must be dissolved in 475 g of methanol to make a 0.250 m solution?1.90 g4.94 g1.19 g2.02 g8.42 g

atroni [7]

Answer:

2.02 g

Explanation:

Molality (m) is the number of moles of solute dissolved in 1 kg (1000 g) of solvent- that is,

$molality = moles of solute ÷ mass of solvent (kg)$

Our first step is to calculate the moles of NH₃ in 475 grams of methanol, using molality as a conversion factor.

0.250 mol/kg × 0.475 kg = 0.119 mol

This solution contains 0.119 moles of NH₃. Now we must convert the moles to grams, using the molar mass of NH₃ as a conversion factor .

17.031 g/mol × 0.119 mol = 2.02 g

Therefore, 2.02 grams of NH₃ must be dissolved in 475 grams of methanol to make a 0.250 m solution.

5 0

4 years ago

The pressure exerted by water at the bottom of a well is 0.50 atm. how many mmHg is this?

mariarad [96]

Answer:

0.5 atm is equal to 380mmHg.

Explanation:

For every 1 atm, it is equal to 760mmHg.

Therefore, 0.5 atm is 760/2, which is 380mmHg.

8 0

4 years ago

Complete this nuclear reaction by selecting which particle would go in the

kompoz [17]

Answer:

Missing particles: $^{0}_{1}e^{+}$ (a positron) and an electron neutrino $\nu_{\rm e}$ .

The nuclear equation would be:

${\rm ^{19}_{10} Ne} \to ^{0}_{1}e^{+} + {\rm ^{19}_{\phantom{1}9}F }+ \nu_{e}$ .

Explanation:

The mass number of a particle is the number on the top-right corner of its symbol.

The atomic number of a particle is the number on the lower-right corner of its symbol.

The nuclear reaction here resembles a beta-plus decay. The mass numbers of the two nuclei are equal. However, the atomic number of the product nucleus is lower than that of the reactant nucleus by $1$ .

A beta decay may either be a beta-plus decay or a beta-minus decay. In a beta-plus decay, a positively-charged positron $^{0}_{1}e^{+}$ and an electron neutrino $\nu_e$ would be released. On the other hand, in a beta-minus decay, a negatively-charged electron $\rm ^{0}_{1}e^{-}$ and an electron antineutrino $\overline{\nu}_e$ would be released.

Electric charge needs to be conserved in nuclear reactions, including this one.

The atomic number of the $\rm Ne$ nucleus on the left-hand side is $10$ , meaning that the nucleus has a charge of $+10$ . On the other hand, the atomic number of the $\rm F$ nucleus on the right-hand side shows that this nucleus carries a charge of only $+9$ .

By the conservation of electric charge, the particles on the right-hand side must carry a positive charge of $+1$ . That rules out the possibility of the combination of one negatively-charged electron $\rm ^{0}_{1}e^{-}$ (with a charge of $-1$ ) and an electron antineutrino $\overline{\nu}_e$ (with no electric charge at all.)