How many valence electrons does antimony (51Sb) have?<\/p>\n\n\n\n
a.<\/p>\n\n\n\n
7<\/p>\n\n\n\n
b.<\/p>\n\n\n\n
2<\/p>\n\n\n\n
c.<\/p>\n\n\n\n
3<\/p>\n\n\n\n
d.<\/p>\n\n\n\n
5<\/p>\n\n\n\n
e.<\/p>\n\n\n\n
4<\/p>\n\n\n\n
1.b<\/p>\n\n\n\n
The correct answer for the addition of 7.5 g + 2.26 g + 1.311 g + 2 g is which of the following to the correct number of significant figures?<\/p>\n\n\n\n
a.<\/p>\n\n\n\n
13.071<\/p>\n\n\n\n
b.<\/p>\n\n\n\n
13<\/p>\n\n\n\n
c.<\/p>\n\n\n\n
13.1<\/p>\n\n\n\n
d.<\/p>\n\n\n\n
13.0<\/p>\n\n\n\n
1.c<\/p>\n\n\n\n
The age of an ancient tree trunk is estimated using radiocarbon dating. If the trunk has a C-14 decay rate that is 6.250% of what it is in living plants, how old is the trunk? The half-life of C-14 is 5,730 years<\/p>\n\n\n\n
The Correct Answer and Explanation is :<\/strong><\/mark><\/p>\n\n\n\n Antimony (Sb) is in Group 15 (also called Group V) of the periodic table, which means it has 5 valence electrons<\/strong>. This is the key factor that determines its ability to form bonds and its chemical behavior.<\/p>\n\n\n\n Correct answer: d. 5<\/strong><\/p>\n\n\n\n When adding measurements, you need to consider the least number of decimal places. Here’s the breakdown:<\/p>\n\n\n\n For addition, the result should have the least number of decimal places, which in this case is 1 decimal place<\/strong> (from 7.5 g). So, rounding the sum to 1 decimal place, the correct result is:<\/p>\n\n\n\n 13.1<\/strong><\/p>\n\n\n\n Correct answer: c. 13.1<\/strong><\/p>\n\n\n\n Radiocarbon dating helps determine the age of a sample by comparing the amount of C-14 remaining in the sample to the original amount in living organisms. C-14 decays over time, and its half-life (the time it takes for half of the C-14 to decay) is 5,730 years<\/strong>.<\/p>\n\n\n\n In this case, the trunk has only 6.250%<\/strong> of the original C-14, meaning 93.75% has decayed<\/strong>. To calculate the age, we need to figure out how many half-lives have passed for the C-14 to decay from 100% to 6.250%.<\/p>\n\n\n\n Using the formula for half-life:<\/p>\n\n\n\n [ Where n<\/strong> is the number of half-lives, and the fraction remaining is 0.06250<\/strong> (since 6.250% is 0.06250 in decimal form). We solve for n<\/strong>:<\/p>\n\n\n\n [ Taking the natural logarithm of both sides:<\/p>\n\n\n\n [ [ So, 4 half-lives<\/strong> have passed.<\/p>\n\n\n\n Now, we multiply the number of half-lives by the length of each half-life to find the age:<\/p>\n\n\n\n [ Thus, the tree trunk is estimated to be about 22,920 years<\/strong> old.<\/p>\n\n\n\n <\/p>\n","protected":false},"excerpt":{"rendered":" How many valence electrons does antimony (51Sb) have? a. 7 b. 2 c. 3 d. 5 e. 4 1.b The correct answer for the addition of 7.5 g + 2.26 g + 1.311 g + 2 g is which of the following to the correct number of significant figures? a. 13.071 b. 13 c. 13.1 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-191524","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/191524","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=191524"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/191524\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=191524"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=191524"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=191524"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\n
\n\n\n\n\n
\n
\n\n\n\n\n
\\text{Fraction remaining} = \\left( \\frac{1}{2} \\right)^n
]<\/p>\n\n\n\n
0.06250 = \\left( \\frac{1}{2} \\right)^n
]<\/p>\n\n\n\n
\\ln(0.06250) = n \\ln\\left(\\frac{1}{2}\\right)
]<\/p>\n\n\n\n
n = \\frac{\\ln(0.06250)}{\\ln(0.5)} \\approx \\frac{-2.7726}{-0.6931} \\approx 4
]<\/p>\n\n\n\n
\\text{Age} = 4 \\times 5730 = 22,920 \\text{ years}
]<\/p>\n\n\n\n